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Please follow the links to view the publication.Nanoelectronics approach based on nano structures & nanomaterial
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0457
This paper gives detailed view on the Nanoelectronics and the approaches adopted for improving the speed of the device without compromising the performance. Performance of the device is mainly based on the speed of operation, Operating voltage and size of the device. In the recent years the two main approaches adopted for optimizing the device performance are new and modified device architectures and using alternate materials which are different from the normal materials used for electronics. Device structures have been modified and designed according to the application. Device modelling is the approach adopted by various companies and research groups in the universities to modify and design new device structures using device modelling and simulation software's. Performance of the device can be improved by using alternate materials such as GaAs, ZnO, BiTe, In, TiO, Fe, Co, Al, Zr etc. Materials other than silicon and germanium with better optoelectronic and electronic properties have been used to improve the performance of the device. The property of the materials can be improved by doping different materials at different compositions and preparing nanomaterials by using different preparation techniques. Materials property is analyzed by using different characterization techniques such as XRD, SEM, TEM, UV, LCR, etc.Radiation enhanced diffusion of implanted palladium in a high-power P-i-N diode
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080189
The influence of annealing temperature (700, 800°C) and implantation dose (1 × 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">13</sup> - 1 × 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">14</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-2</sup> ) of 9.5 MeV Pd on the subsequent Radiation Enhanced Diffusion (RED) is studied in the range of optimal diffusion temperatures (550, 600, 650°C)for the electrical parameters of a power P-I-N diode. Spreading resistance measurements have shown that the Pd dose of 1 × 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">14</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-2</sup> is capable to compensate the anode doping profile in the N-base close to the anode junction similar to that of the RED from sputtered Pd. Contrary to the devices with sputtered Pd, the reproducibility of this process is lower and the radiation damage from the Pd implantation compensates the high doped P layer up to the Pd range (≈ 3.5 μm). The dependences of leakage, carrier lifetime, forward voltage drop and reverse recovery on the process parameters of the Pd layer are shown for 2.5 kV/100 A diode.Analysis of the doping fluctuation on robustness of ESD protection devices
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080207
Electrostatic discharge (ESD) is a major threat to the reliability of integrated circuits, where approximately 20% of total integrated circuit (IC) failures are due to ESD. Discharge of charged objects or human discharge into IC chip pins with very high currents (up to 10 A) in a short time period (1 ns to 200 ns) causes serious damage to the very sensitive devices of the circuitry. This may happened during manufacturing, assembly, shipment, and in the field. Since the phenomenon is unavoidable, there is a strong need of developing proper strategies to protect the functional devices, circuits and systems. In this paper we present the analysis of the ESD protection structure supported by the advanced 2-D mixed mode electro-thermal device and circuit simulation.Local donor doping by proton implantation in p<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>nn<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> diodes fabricated on different silicon substrates
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080182
The effect of excess donor doping introduced by implantation with 700 kV and 1.8 MeV protons and subsequent annealing up to 550°C in silicon substrates with different oxygen content was investigated. Three different types of silicon material were chosen for this purpose: Czochralski, oxygen-lean and oxygen rich float-zone silicon. Deep and shallow levels resulted from implantation and subsequent annealing were studied by deep level transient spectroscopy and C-Vprofiling. Results show that hydrogen donors appear at the proton end-of-range after implantation in all materials. Their introduction rate depends linearly on proton fluence and is substantially higher in Czochralski and oxygen-rich float zone materials due to higher oxygen concentration. It is shown that during post-implantation annealing, the excess donor doping changes in several phases. Hydrogen donors anneal out above 250°C and then, hydrogen-related thermal donors and thermal donors are generated. When annealing temperature exceeds 400°C, the hydrogen thermal donors are still localized at the proton end-of-range in oxygen-lean float zone silicon while in Czochralski silicon and oxygen-rich float zone material, thermal donors arise in the whole bulk and radiation enhanced thermal donors decorate the profile of radiation damage. The level of local doping by hydrogen thermal donors is proportional to implantation fluence and layers are stable up to 550°C for implantation fluences above 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">13</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-2</sup> . The detrimental effect of hydrogen donors and thermally activated donors on blocking characteristics of power p<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>nn<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> diodes is also discussed.Theoretical evaluation of maximum doping concentration, breakdown voltage and on-state resistance of field-plate compensated devices
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080183
The idealised on-state resistance vs. breakdown voltage behaviour for field-plate compensated devices is analysed for different impact ionisation models. For small device dimensions, we found a significant deviation from common values of maximum doping concentration due to an overestimated impact ionisation coefficient at higher electric fields. This, in turn, leads to a lower doping density and higher on-state resistance compared to the optimal values.Analysis of field-plate LDMOS devices for RF applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080226
One of the design difficulties found in SJ power RF LDMOS transistors is the P/N pillars doping inter- diffusion which increases with the lateral diffusion factor and degrades the device R<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">ON-sp</sub>. An alternative 3-D RESURF method consists on placing a trench oxide of predetermined thickness together with a grounded polysilicon layer inside the trench along the LDD region to replace the P pillar of the SJ LDMOS. The metal-thick-oxide block acts as a field-plate (FP), enhancing the 3-D RESURF lateral depletion which allows increasing the N-drift doping concentration. In order to study the feasibility of applying the FP concept in RF LDMOS transistors a preliminary analysis has been performed to compare the performance of SJ LDMOS with the proposed FP LDMOS structure in terms of drift region resistance (R<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">LDD</sub>), voltage capability (V<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">BR</sub>) and transconductance (g<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">m</sub>) by means of theoretical analysis and extensive 2-D numerical simulations.The controlled punch through (CPT) IGBT the next step in buffer optimization for thin wafer technology
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080221
The controlled punch through (CPT) IGBT buffer is discussed as a mean for the reduction of wafer thickness down to the theoretical limit of the next generation 1200 V IGBT. The CPT buffer occupies a small fraction of the silicon and at the same time provides a high degree of freedom in the design of the anode doping profile to maintain all relevant electrical parameters within a given specification. While presented for 1200 V IGBTs, the new buffer concept can also be applied with advantages to any voltage class. Beside the reduced ON-State losses, the IGBT maintains good blocking, soft turn-off, wide SO A and very good short circuit capability. This is shown theoretically and proved experimentally.Estimation of threshold voltage and subthreshold slope of extremely scaled DFG MOSFETs
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070734
A two-dimensional (2-D) analytical expression for the surface potential and a mathematical relation for the calculation of the threshold voltage Vt and subthreshold slope S of symmetric double-gate (DG) n-MOSFETs have been derived taking into account the effect of bandgap narrowing due to heavy channel doping and quantum-mechanical (QM) effects. The DG MOSFET has been simulated using the device simulator ATLAS and the simulation values of Vt and S have been extracted for different values of structural dimensions, channel doping concentrations and gate materials. Our analytical results have been validated with 2-D numerical simulation data. Calculated data match well with the simulation results for various devices ensuring the validity of our model.Ru-doped semi-insulating buried heterostructure laser operating up to 100°C for 10-Gbit/s direct modulation
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050485
We report the high-temperature characteristics of 1.3-μm InGaAsP directly modulated lasers with a simple buried structure using Ru-doped semi-insulating InP. Clear eye openings under 10-Gbit/s direct modulations were obtained from 0°C to 100°C. (2 pages)SIMOX
http://dl-live.theiet.org/content/books/cs/pbep004e
<p xmlns="http://pub2web.metastore.ingenta.com/ns/">SIMOX represents the first effort to compile a broad spectrum of knowledge from various groups of researchers and technologists in the world. It provides the reader with a basic understanding of SIMOX technology and in addition gives a good starting point for further investigation and applications.</p>Photonically tuned patch and dipole millimetre wave arrays using selectively doped semiconductor wafers
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010296
We present results from a previous study into the manipulation of the transmission response arising from an array of doped elements within a semiconductor wafer. If a periodic array is formed by doping, within a semiconductor slab of suitable resistivity, then a resonant effect is produced when a plane wave is incident on the sample. The performance of this array can be very close to that of a conventional frequency selective surfaces (FSS) provided the doping levels are high enough. Results are presented from a new study we have carried out to investigate the tuning effect of an incident photonic beam on a predetermined array of doped elements within a semiconductor wafer. When photons of suitable wavelength are incident on a semiconductor the photoconductive nature of the semiconductor renders it more conducting than in the dark state and we use this property in this study. An optical mask is used whereby the wafer is only exposed to the optical beam through the transparent regions of the mask. In this way the performance of the array can be controlled and tuned over a range determined by the dimensions of the mask used. We have previously used this technique to successfully generate inductive grid arrays within a silicon wafer.Soft reverse recovery power diodes diffused with iridium
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960889
It is shown that iridium diffusion can be used as an alternative technique for fabrication of diodes with suitable carrier lifetime gradient in the base, resulting in relatively soft reverse recovery characteristics.Carrier lifetime control: processes and modelling
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960861
Currently, design software for power semiconductor devices can only represent carrier lifetime control in the crudest of ways, and there is a growing need for better design tools to enable easier process selection, more tightly focused test matrices and a reduction in developments costs for new products. In this paper we discuss new-generation doping and irradiation technologies and possible modelling approaches aimed at improving the design process. (3 pages)Raman imaging as a structural probe for silicon structures
http://dl-live.theiet.org/content/conferences/10.1049/ic_19951467
The Microline Focus Spectrometer (MiFS) instrument is capable of obtaining Raman spectra from a surface with sub-micron resolution and can generate profiles and images representing intensity (species concentration), frequency (stress) and bandwidth (crystallinity). This approach is an objective compromise between the time consuming and high positional stability demands of point by point sampling of the surface and the spectroscopically limited global illumination method. In addition the method does not rely upon moving optical components and thus is inherently stable. An essential element of Raman imaging is the ability to achieve a direct registration of the Raman image with a reflected light image. This is easily achieved using the MiFS approach, either by generating an image in reflected laser light from the surface as a separate experiment or by collecting reflected laser plasma line intensity simultaneously with the Raman image data. Raman images are shown from an experimental silicon structure with groups of alternate stripes of oxide and nitride on the surface. The images clearly reveal a marked change from tensile to compressive stresses as the stripe spacing is reduced to 0.5 μm. Closer analysis shows more complex variations in shift and bandwidth across and between the stripes. Silicon etching to produce complex microstructures is controlled by etch stop boundaries of boron doped silicon. Diffusion of boron into the silicon matrix results in Raman shift and bandwidth changes as the silicon lattice is adjusted to accommodate the B atoms. Raman mapping of the cross sectional edge of a silicon wafer, which has been subjected to 2 hours of B diffusion, is shown. Both the Raman shift and bandwidth images show the B doped region extending 4.5 μm into the silicon surface. (3 pages)Improved base current ideality in polysilicon emitter bipolar transistors by fluorine implantation
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950179
In this paper we have shown that the presence of fluorine in a polysilicon emitter bipolar transistor can result in several important benefits. We have shown that in devices where the emitter/base junction depth is very shallow, the presence of fluorine results in an improved base current ideality factor, in both npn and pnp polysilicon emitters. For example, in npn polysilicon emitters given an emitter drive-in of 10 seconds at 1025°C, an improvement in ideality factor from 1.19 without a fluorine implant to 1.03 with a fluorine implant. Further, in the similarly treated pnp polysilicon emitters, a reduction in base current for all values of V<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">BE</sub> was observed, by at least a factor of 2. In contrast, in devices where the emitter/base junction depth was not as shallow, a reduction in emitter resistance was observed. For example, in npn polysilicon emitter devices given an emitter drive-in of 60 minutes at 900°C, a drop in interfacial resistivity from 23.5 Ωμm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> for unimplanted devices to 12.5 Ωμm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> for fluorine implanted devices. This drop in emitter resistance is consistent with enhanced break up of the interfacial oxide layer. (5 pages)P<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>/N shallow junctions formation on Ge<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> preamorphized silicon substrate
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950186
Ultra shallow P<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>/N junctions obtained by low energy boron implantation in a preamorphized silicon substrate are characterized. The preamorphization stage is accomplished by implanting high dose of germanium ions under well defined conditions of temperature and energy. As a result, the suppression of channelling tails, and the high degree of electrical activation of the boron after low temperature solid phase epitaxial (SPE) regrowth have been clearly demonstrated. Combining XTEM analysis, SIMS profiling, spreading resistance method and electrical noise measurements allowed us to characterize the preamorphization in terms of its effect on the structural and electrical properties of the P<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>/N junctions. Correlation between the preamorphization induced defects (End-Of-Range) and the junction leakage current has been established. We show that, when these defects are located in the space charge region, they act as generation-recombination centres and increase, by the way, the electrical noise on the forward current of the diodes. (6 pages)Analysis and simulation of insulated gate bipolar transistor with buffer n'-layer
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940934
This paper presents the results of analysis and simulation of the static characteristics of IGBTs with a buffer n'-layer. In their investigation, the authors have used the “Issledovanie” software package intended for numerical simulation of the static and dynamic characteristics of silicon power devices. This program is based on the numerical solution of the fundamental set of equations taking into account the total amount of physical phenomena (electron-hole scattering, dependence of lifetime and mobility on doping concentration, band-gap narrowing, Auger recombination etc.). The authors also present the results obtained within a simple analytical model.N, C-codoped BiOCl flower-like hierarchical structures
http://dl-live.theiet.org/content/journals/10.1049/mnl.2012.0496
N, C-codoped BiOCl (BiOCl–NC) flower-like hierarchical structures were synthesised by an one-pot solvothermal process and characterised by X-ray diffraction patterns, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, transmission electron microscopy and high-resolution transmission electron microscopy. As-synthesised BiOCl–NC showed higher photocatalytic activity in an aqueous RhB photodegradation system than pure BiOCl under visible light irradiation. The trapping experiments of active species during the photocatalytic reaction showed that the photocatalytic degradation of organic pollutants in the BiOCl–NC system proceeds through direct hole transfer and O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">•−</sup> rather than •OH.Influence of Al nitrate and Al chloride doping sources on structural and optical properties of sol–gel derived Al:ZnO nanoparticles
http://dl-live.theiet.org/content/journals/10.1049/mnl.2012.0197
Al-doped ZnO nanoparticles have been synthesised via sol–gel method. Aluminum nitrate and aluminum chloride, as two widespread doping sources, have been compared in various Al/Zn molar ratios of 0.1, 0.5, 1, 2 and 5. After sol preparation, all samples with different Al content have been aged and then dried at 120°C. The resultant grinned powders calcined at different temperatures of 400, 500, and 600°C. X-ray diffraction (XRD) method has been used to investigate crystallisation behaviour and structural properties of samples. Less crystallinity in chloride source samples is detected compared to the nitrate source; however, identical distortion of hexagonal wurtzite unit cell in both sources was evident in XRD results. Field emission scanning electron microscopy demonstrates semisphere morphology of ZnO nanoparticles with particle size less than 60 nm. Fourier transform infrared spectroscopy was conducted to find possible chemical reactions and complexes during the sol–gel process in different Al source samples. UV-vis spectroscopy was carried out to find optical properties of the Al:ZnO samples. The results represent different optical properties in Al chloride and Al nitrate sources.Recent progress and current issues in SiC semiconductor devices for power applications
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20010166
A review of current issues in SiC device processing technology is followed by a critical assessment of the current state-of-the-art and future potential for SiC power devices. Material quality, ion implantation, the SiC–SiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> interface and the thermal stability of contacting systems are all identified as requiring further work before the full range of devices and applications can be addressed. The evaluation of current device technology reveals that SiC Schottky and PIN diodes are already capable of increased power densities and substantially improved dynamic performance compared to their Si counterparts. Although direct replacement of Si devices is not yet economically viable, improvements in system performance and reductions in total system cost may be realised in the short term. Widespread use will, however, require continued improvements in wafer quality while costs must fall by a factor of ten. Finally, the development of new and improved packaging techniques, capable of handling increased die temperature and high thermal cycling stresses, will be needed to fully exploit the potential of SiC.Large-area shower implanter for thin-film transistors
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_19949826
Solid-state diffusion and conventional ion implantation are not suitable for source and drain regions formation of polysilicon thin-film transistors on glass substrates. A 30 cm diameter large-area low-energy ion shower implanter with RIPE ion source and double-grid extraction system was developed as a possible low-cost solution. The ion beam current density for hydrogen plasma was 100 µA/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> for 3 keV implant energy, 300 W RF power, 140 gauss magnetic field and 3*10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-4</sup> mbar pressure. The uniformity of beam current density over the central 20 cm diameter was ±3.5%. Phosphorus implantation has been performed using a 15% PH<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> in H<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> gas mixture. Implantation at 3 keV for 5 min. results in an integrated dose of 2.48*10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">16</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-2</sup> with the concentration peak at a depth of 8.3 nm. Planar and mesa diodes fabricated on p-type silicon substrates have yielded fine rectifier characteristics. The shower implanter is thus suitable for TFTs source and drain region formation.Study of intermixing in InGaAs/(Al)GaAs quantum well and quantum dot structures for optoelectronic/photonic integration
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20045053
Two of the most important intermixing techniques, ion implantation and impurity free vacancy disordering, are investigated and compared in InGaAs/(Al)GaAs quantum well (QW) and quantum dot (QD) structures. For ion implantation induced intermixing, arsenic implantation was performed and the amount of interdiffusion created was found to vary as a function of implantation dose and temperature. Impurity free vacancy disordering was also enhanced by deposition of SiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> in both QW and QD structures and annealing at different temperatures. In order to obtain large differential energy shifts for device integration using both methods, the essential issue of suppression of thermal interdiffusion using a TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> capping layer was also addressed.Leakage power analysis and reduction: models, estimation and tools
http://dl-live.theiet.org/content/journals/10.1049/ip-cdt_20045084
The high leakage current in the nanometre regime is becoming a significant proportion of power dissipation in CMOS circuits as threshold voltage, channel length and gate oxide thickness are scaled. Consequently, the identification and estimation of different leakage currents are very important in designing low power circuits. In the paper a methodology for accurate estimation of the total leakage in a logic circuit based on the compact modelling of the different leakage currents in nanoscaled bulk CMOS devices is demonstrated. Different leakage currents are modelled based on the device geometry, 2-D doping profile and operating temperature. A circuit level model of subthreshold, junction band-to-band tunnelling (BTBT) and gate leakage is described. The presented model includes the impact of quantum mechanical behaviour of substrate electrons on the circuit leakage. Using the compact current model, a transistor has been modelled as a sum of current sources (SCS). The SCS transistor model has been used to estimate the total leakage in simple logic gates and complex logic circuits (designed with transistors of 25 nm effective length) at room and elevated temperatures.Modelling of doping-dependent subthreshold swing of symmetric double-gate MOSFETs
http://dl-live.theiet.org/content/journals/10.1049/iet-cds.2009.0201
A simple, yet efficient two-dimensional (2D) model for the doping-dependent subthreshold swing characteristics of symmetric double-gate (DG) MOSFETs has been presented. The 2D Poisson's equation has been solved by using parabolic potential approximation method to obtain the 2D channel potential function of the device. A closed-form expression for the doping-dependent effective current conducting path distance (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">d</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">eff</sub>) measured with respect to the centre of the channel of the symmetric DG MOSFET has been presented. Finally, the closed-form expression of the conducting path distance parameter <i xmlns="http://pub2web.metastore.ingenta.com/ns/">d</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">eff</sub> has been utilised to obtain the subthreshold swing model of the device. The validity of the proposed model has been shown by comparing the analytical results with numerical simulation data obtained by using the commercially available ATLAS™ device simulator.Investigation of GaAs homojunction bipolar transistor with delta doping emitter structure
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_19952201
A GaAs homojunction bipolar transistor with a delta doping emitter structure is proposed and demonstrated. The proposed device makes use of a delta doping structure inducing a triangular barrier for minority carrier confinement, resulting in a high emitter injection efficiency. Based on the minority carrier transport in the bulk emitter region with drift-diffusion mechanisms, and in the triangular barrier region with tunnelling and thermionic-emission mechanisms, an analytical derivation of current-voltage characteristics, including the effect of bandgap shrinkage, was obtained. The calculated results show that the triangular barrier is the key parameter in determining the electrical properties. In addition, due to the absence of heterojunction, the proposed device exhibits more nearly constant current gain with collector current than for the AlGaAs/GaAs heterojunction bipolar transistor (HBT). The proposed device, grown by molecular beam epitaxy, shows a differential current gain of 13 and an offset voltage of 60 mV at a base-to-emitter doping ratio of 10. The offset voltage is attributed mostly to the geometric limits. With a simple chemical treatment of Na<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>S.9H<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O, the differential current gain is enhanced to be 16 due to the reduced surface recombination. Theory and experiment indicate the potential application of the proposed device.In-situ phosphorous-doped VLPCVD polysilicon layers for polysilicon thin-film transistors
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_19949827
Polysilicon devices on glass substrates for large-area applications, such as poly-Si thin-film transistors in active-matrix displays, need a complete low-temperature process, especially to fabricate the drain and source polysilicon layers as well as the active channel layer. For this purpose, we have developed a very low pressure chemical vapour deposition process allowing in-situ phosphorous doping. By varying total pressure and phosphine/silane ratio, we control the doping concentration level over a large range (10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">18</sup> to 5*10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">20</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-3</sup>). Depending on deposition conditions, films are first amorphous or partially crystallised. The films are then fully crystallised by a 12 h in-situ vacuum annealing at 600 degrees C. They are physically and electrically characterised. It is observed that in the 30 to 90 pascal pressure range, the dopant activation rate, electrical carrier mobility, and conductivity of the layers are optimised whatever the doping level. First runs of low temperature processed TFTs involving in-situ highly doped source and drain layers have given promising results.Effects of different buffer structures on the avalanche behaviour of high voltage diodes under high reverse current conditions
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20050060
The effects of different buffer structures on the avalanche and post avalanche behaviour of high voltage silicon diodes under high reverse current conditions has been investigated. After the onset of avalanche, when the diodes are reverse biased, branches both with positive and negative differential resistance may occur in the device characteristics and depend sensitively on the doping profile of the buffer layer. By numerical device simulation the influence of relevant bulk doping and various buffer profiles on these static reverse characteristics are analysed to understand, clarify and illustrate the breakdown behaviour of high voltage <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i>-diodes. Based upon these considerations an effective restriction of the electric field maximum at the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">nn</i>+-junction at the cathode side of the diode can be achieved by adapting the doping gradient of the buffer profile.Local lifetime control in silicon power diode by ion irradiation: introduction and stability of shallow donors
http://dl-live.theiet.org/content/journals/10.1049/iet-cds_20070013
Enhanced formation of shallow donors (SDs) in hydrogen or helium-irradiated and subsequently annealed float‐zone n-type silicon is investigated. Ion energies, irradiation fluences and annealing temperatures were chosen in ranges typically used for local lifetime control in silicon power devices. Introduced radiation defects and SDs were investigated by deep-level transient spectroscopy and C–V profiling. Results show that radiation damage produced by helium ions remarkably enhances formation of thermal donors (TDs) when the annealing temperature exceeds 375°C, i.e. when the majority of vacancy-related recombination centres anneal out. Proton irradiation introduces hydrogen donors (HDs) which form a Gaussian peak at the proton end-of-range. Their concentration linearly increases with proton fluence and changes dramatically during post-irradiation annealing between 100 and 200°C since HD constituents are reacting with radiation damage. Their annealing in this temperature range is influenced by the electric field. If annealing temperature exceeds 400°C, HDs disappear and the excessive shallow doping is caused, as in the case of helium irradiation, by TDs enhanced by radiation damage. Shallow doping introduced by both hydrogen and helium can have a detrimental influence on blocking voltage of power diodes if high irradiation fluences or wrong annealing conditions are chosen.Synthesis of p-type ZnSe nanowires by atmosphere compensating technique
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0219
The atmosphere compensating technique with an individual selenium source is, first, used in the growth of phosphorus-doped p-type ZnSe nanowires. The morphology and structure characterisations reveal that the as-synthesised ZnSe nanowires have a wurtzite structure with a diameter of about 160 nm, a growth direction of [001]. The electrical properties’ characterisations demonstrate that the selenium atmosphere compensation technique assisted with phosphorus-doping leads to a substantial action in p-type conductivity of ZnSe nanowires with a high mobility of 1.25 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> V<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> S<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> and carrier concentration of 1.47×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">18</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−3</sup>. The photoluminescence measurements show a dominant emission and two donor–acceptor pair emission.Scaling properties of In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.7</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.3</sub>As buried-channel MOSFETs with atomic layer deposited gate dielectric
http://dl-live.theiet.org/content/journals/10.1049/el.2010.2960
Deep-submicron In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.7</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.3</sub>As buried-channel MOSFETs with various gate lengths down to 40 nm are demonstrated. In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.7</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.3</sub>As buried-channel MOSFETs were fabricated on an epitaxial wafer using an InP/In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.52</sub>Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.48</sub>As double barrier. The device characteristics were analysed, including subthreshold swing, transconductance and drive current. Good scaling behaviour was observed for these III–V MOSFETs. For a 40 nm gate length device, the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>T</i></sub> roll-off is around 100 mV, the subthreshold swing is 132 mV/dec and DIBL is 214 mV/V.Dual carbon effect on electrical properties of high dose indium implants in silicon
http://dl-live.theiet.org/content/journals/10.1049/el_20053455
A novel aspect of the carbon effect on indium electrical activation in silicon is presented. It is shown that, depending on the thermal budget used during annealing, the presence of carbon can increase or inhibit the indium electrical activation. The different behaviour is explained in terms of the In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">s</sub>–C<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">s</sub> couple formation for low thermal budgets and carbon precipitation for high thermal budgets.Laterally stacked varactor formed by ion implantation
http://dl-live.theiet.org/content/journals/10.1049/el_19990579
Laterally stacked varactor formed by ion implantation Planar, MMIC compatible, multi-junction varactors have been fabricated using a single <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-type epitaxial layer followed by multiple energy Mg<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> ion implantation. The junctions, numbering between 1 and 4 (= <i xmlns="http://pub2web.metastore.ingenta.com/ns/">N</i>), were formed laterally by selective implantation masking. Current-voltage measurements of the devices show the benefits of the stacking with breakdown voltage almost proportional to <i xmlns="http://pub2web.metastore.ingenta.com/ns/">N</i>.Tunable bandgap opening in the proposed structure of silicon-doped graphene
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0195
A specific structure of doped graphene with substituted silicon impurity is introduced and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">ab initio</i> density-functional approach is applied for the energy band structure calculation of the proposed structure. Using the band structure calculation for different silicon sites in the host graphene, the effect of silicon concentration and unit cell geometry on the bandgap of the proposed structure is also investigated. Chemically, silicon-doped graphene results in an energy gap as large as 2 eV according to density-functional theory calculations. As the authors will show, in contrast to previous bandgap engineering methods, such structure has significant advantages including wide gap tuning capability and its negligible dependency on lattice geometry.Gate overlap length reduction and shallow junction formation in high-performance fine MOSFETs by ion implantation through thin oxide film
http://dl-live.theiet.org/content/journals/10.1049/el_19981653
A gate overlap length of only 16 nm between the gate and the source/drain has been achieved in fine <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-type metal oxide semiconductor field effect transistors with 0.1 µm gate length by arsenic ion implantation through a thin oxide film formed by chemical vapour deposition. The presented technique enables the gate overlap length to be reduced by less than half of the value for conventional lower energy implantation while maintaining a shallow junction depth for the source/drain.Implantation approach to SEU suppression in GaAs
http://dl-live.theiet.org/content/journals/10.1049/el_19990512
It is shown that oxygen-implanted GaAs with oxygen concentrations of 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">20</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">–3</sup> (or 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">19</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">–3</sup> if co-implanted with Al), annealed in the 500 – 850°C temperature range, can result in highly resistive layers with subpicosecond free-carrier lifetimes. It is suggested that such layers can be used to suppress single event upsets (SEUs) in GaAs digital circuits.Analysis of reverse tunnelling current in GaInN light-emitting diodes
http://dl-live.theiet.org/content/journals/10.1049/el.2010.3236
The characteristics of the reverse leakage current of GaInN/GaN multiple quantum well light-emitting diodes (LEDs) are examined with various <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-type GaN doping concentrations and interpreted by using a tunnelling current model. Changing the doping concentration of the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-type GaN influences the tunnelling probability of electrons into the conduction band and thus the reverse leakage current. Reducing the doping concentration of the top 150 nm portion of the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-type GaN layer by half decreases the tunnelling probability, resulting in decrease of the reverse leakage current by 80% at −10 V without deterioration of any forward electrical properties of LEDs.Selective Si interdiffusion into ion implanted GaAs from SiN and its application to GaAs MESFET
http://dl-live.theiet.org/content/journals/10.1049/el_20020302
Selective Si interdiffusion into ion implanted GaAs from SiN encapsulation was observed and a GaAs MESFET with a highly conductive layer was developed using the interdiffusion. During the annealing of implanted <sup xmlns="http://pub2web.metastore.ingenta.com/ns/">29</sup>Si at 950°C, Si was selectively diffused into the ion implanted region from SiN encapsulation and formed a highly conductive layer near the surface. The diffused Si improved the ohmic contact resistivity and electrical characteristics of the MESFET.In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.53</sub>Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.22</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.25</sub>As/InP heterojunction bipolar transistor with δ-doped continuous-conduction-band (CCB) structure
http://dl-live.theiet.org/content/journals/10.1049/el_19990220
A new In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.53</sub>Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.22</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.25</sub>As/InP heterojunction bipolar transistor with a δ-doped continuous-conduction-band (CCB) structure has been fabricated successfully and studied. The use of the δ-doped CCB structure can effectively eliminate the potential spike in the E-B heterojunction. An offset voltage as low as 50 mV and a relatively high current gain of 80 have been obtained experimentally. The studied device is therefore promising for practical circuit applications.Carrier and mobility profiling of ultra-shallow junctions in Sb implanted silicon
http://dl-live.theiet.org/content/journals/10.1049/el_20040493
Differential Hall effect measurements have been carried out to obtain electron concentration and mobility profiles for 2 keV implants of 1×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">15</sup> Sb<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−2</sup> in 〈100〉 silicon with nanometre resolution. A comparison is made between carrier and atomic profiles determined using secondary ion mass spectroscopy.Modifying functionality of variable optical attenuator to signal monitoring through defect engineering
http://dl-live.theiet.org/content/journals/10.1049/el.2010.2785
A commercial silicon-based variable optical attenuator has been converted to a low bandwidth (quasi-CW) light monitor through an ion implantation and annealing process. The measured total optical loss of the device is <5 dB while the responsivity per tapped fraction is 1 mA/W/dB. The straightforward manner in which the monitoring functionality is induced suggests a cost-effective route to CW optical monitors using a widely available commercial product.First epitaxial <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pnp</i> bipolar transistor on diamond with deep nitrogen donor
http://dl-live.theiet.org/content/journals/10.1049/el_19991201
Vertical <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pnp</i> bipolar transistors on diamond have been fabricated by doping the base with deep nitrogen donor (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">E<sub>C</sub></i> – <i xmlns="http://pub2web.metastore.ingenta.com/ns/">E<sub>D</sub></i> = 1.7 eV). The <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pn</i> junction formed by the nitrogen donors and boron acceptors was confirmed. Transistor characteristics in common-emitter and common-base modes were measured at room temperature.Influence of Zn doping profiles on excitation dependence of photoluminescence intensity in InGaAsP heterostructures
http://dl-live.theiet.org/content/journals/10.1049/el_20052347
It is known that the Zn doping profile in strained multi-quantum-well (MQW) InGaAsP lasers strongly affects the electro-optical characteristics of these devices and their temperature sensitivity. A systematic investigation of the excitation dependence of the active layer photoluminescence (PL) intensity from compressively strained InGaAsP MQW <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> laser material with different Zn doping profiles is described. When the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pn</i> junction lies within the active region, the excitation dependence of the PL intensity is superlinear at low excitation and linear at higher excitation. As the Zn profile is set back from the heterointerface creating a displaced <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pn</i> junction from the active region, the excitation dependence is superlinear and linear at 300 K but becomes linear for all excitation powers at 77 K. The implications of these observations are discussed.P/He ion implant isolation technology for AlGaN/GaN HFETs
http://dl-live.theiet.org/content/journals/10.1049/el_19980091
A novel process for the isolation of AlGaN/GaN HFETs is reported, utilising co-implantation of phosphorus and He ions. After implantation the material sheet resistance is > 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">8</sup> Ω/□, even at temperatures as high as 200°C. The high resistance is maintained for high temperature anneals > 700°C. HFETs fabricated with this procedure exhibit good characteristics.Suppression of reverse-short-channel effect in sub –0.1 µm <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-MOSFETs with Sb S/D implantation
http://dl-live.theiet.org/content/journals/10.1049/el_19990325
A study is presented into the reverse-short-channel effect (RSCE) for Sb S/D ion implantation at 10 keV. A high impurity concentration is found to reduce interstitial movement in the channel, which restricts the level RSCE at short-channel lengths. The interstitials can be healed by thermal treatment at 850°C directly after ion implantation, resulting in the suppression of the RSCE.Synthesis, structural and optical properties of water-soluble Mn-doped CdS nanocrystals
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0016
Water-soluble Mn-doped CdS nanocrystals were synthesised by an aqueous colloidal synthetic technique. X-ray diffraction identifies that the Mn-doped CdS nanocrystal is a cubic structure without impurity phase. Transmission electron microscopy suggests a narrow size distribution of the nanocrystals with an average particle size of ∼3.6 nm. Moreover, UV–vis absorption and photoluminescence (PL) spectra of the nanoparticle were also measured. PL results show that Mn-doped CdS nanocrystals have a distinct Mn<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2+</sup> related emission well-separated from the trap state emission. Reaction variables such as the 3-Mercaptopropionic acid/Cd (MPA/Cd) ratio, reaction temperature and Mn<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2+</sup> doped concentration were systematically investigated to evaluate the impact of these variables on particle size and optical property. The results indicate that the 2 mol% Mn-doped CdS nanocrystals synthesised at 70°C and the MPA/Cd ratio of 3.5 have the highest PL intensity.High performance CSTBT with p-type buried layer
http://dl-live.theiet.org/content/journals/10.1049/el.2012.0220
A novel high performance carrier stored trench bipolar transistor (CSTBT) with a p-type buried layer (PBL-CSTBT) is proposed. The p-type layer of the structure is formed by ion implantation at the bottom of the trench after a partial etching of the P<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">base</sub>/N<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">cs</sub> layer and the fabrication process is fully compatible with the conventional CSTBT (C-CSTBT) structure. In comparison with the C-CSTBT without a buried layer, the novel structure offers not only high breakdown voltage, but also improved E<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">off</sub>-V<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">ce(on)</sub> trade-off characteristics.<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-type conduction above room temperature in nitrogen-doped ZnO thin film grown by plasma-assisted pulsed laser deposition
http://dl-live.theiet.org/content/journals/10.1049/el_20062161
Nitrogen-doped ZnO thin films were deposited using the pulsed laser deposition technique. The epitaxial ZnO films were <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-type in the measured temperature range 200–450 K, with hole concentrations and mobilities of 9.6×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">15</sup> cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−3</sup> and 10.8 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>/V-s, respectively, at room temperature. The films remained <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-type under conditions of changing illumination. This result represents a step towards realisation of ZnO-based optoelectronic devices for high-temperature operation.Improvement of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f<sub>T</sub></i> by dipole doping at the collector heterojunction in InP double HBTs
http://dl-live.theiet.org/content/journals/10.1049/el_19970644
The authors show clearly how dipole doping at the collector heterojunction in an InP/InGaAs double heterojunction bipolar transistor improves device performance. Specifically, both <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f<sub>T</sub></i> and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f<sub>MAX</sub></i> are increased and the DC current-blocking is reduced. Also the DC switching characteristics, seen in devices with abrupt undoped InGaAs/InP collector heterojunctions, can almost be eliminated by using the dipole doping at that interface.Integration of n- and p-channel InGaP/InGaAs doped-channel pseudomorphic HFETs
http://dl-live.theiet.org/content/journals/10.1049/el_20070621
n- and p-channel InGaP/InGaAs doped-channel pseudomorphic HFETs on the identical chip by selectively etching process are first demonstrated. Particularly, the saturation voltage of the n-channel device is relatively small because 2DEG is formed and modulated in the InGaAs strain channel. Experimentally, an extrinsic transconductance of 292 (72) mS/mm and a saturation current density of 335 (−270) mA/mm are obtained for the n-channel (p-channel) device. Furthermore, the integrated devices exhibit broad gate voltage swings for linear and signal amplifier applications.Reliable lifetime prediction in deep submicrometre P-channel partially depleted SOI MOSFETs
http://dl-live.theiet.org/content/journals/10.1049/el_19980455
Two-stage hot-carrier-induced degradations are thoroughly investigated in deep submicrometre partially depleted P-channel SIMOX MOSFETs. A reliable method for lifetime prediction is proposed for a wide gate length range. The saturation level between the power and logarithmic laws, which depends on the various degradation mechanisms, plays an important role in device lifetime prediction.