New Publications are available for Radiation effects (semiconductor technology)
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New Publications are available now online for this publication.
Please follow the links to view the publication.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 power devices breakdown behaviour by ion beam and electron beam induced charge microscopy
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080194
The development of appropriate edge termination structures is a challenging task for all kinds of different vertical power semiconductors such as high-voltage diodes, IGBTs or especially compensation devices. Ion-beam induced charge microscopy and electron-beam induced charge microscopy are reliable tools for imaging of space-charge regions and detection of electric-field enhancements inside of power devices. The usefulness of these methods is shown for the example of high-voltage power diodes and low-voltage power MOSFET. Advantages and limitations of the measurement techniques are discussed.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.SEE analysis and mitigation for FPGA and digital ASIC devices
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050514
A collection of slides from the author's conference presentation is given. (8 pages)BAE Systems, air systems, approach to the problem of atmospheric radiation
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050513
The BAE Systems, air systems, approach to the problem of atmospheric radiation is presented and practical methods discussed. The ground based neutron testing work package for SPAESRANE is led by BAE Systems. The practicalities of real systems testing at Los Alamos (USA), the Tri-University Meson Facility (Canada) and the Theodor Svedberg Laboratory (Sweden) are discussed. BAE Systems have been interested in the field of weightless neural networks for many years, because of their simplistic/natural resilience to corruption and erroneous information. This has led to the development of several weightless non-neural based weightless binary architectures which are currently being studied for their resilient properties with a view of offering protection to avionics systems. (19 pages)Observations of SEE phenomena using CCDs: "seeing SEEs"
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050510
Cosmic-radiation-induced single event effects (SEEs) in avionics are largely due to secondary neutrons generated when primary cosmic ray particles interact with atmospheric molecules. They occur when high-energy neutrons cause bursts of spurious charge through interactions with atomic nuclei in electronic devices. This behaviour can result in a range of upset mechanisms including memory state inversion, avalanche breakdown, and latch up. This presentation describes the results of recent work using imaging charge-coupled devices (CCDs) to study the transient charge generated in a silicon lattice during neutron-induced SEEs. This technique permits SEEs to be directly observed with high spatial resolution, allowing the shape of generated charge clouds to be determined. Results were presented from experiments performed during accelerated testing in simulated atmospheric neutron spectra. Analysis of the SEE image data was described. Information of considerable scientific and technological interest can be extracted from these data; examples given in this presentation includes classification of event species and derivation of single event upset (SEU) multiplicity statistics, both of which require the spatial information which CCDs provide. Development of an imaging cosmic radiation monitor, to observe SEE phenomena in the natural environment, was described. (14 pages)Laser simulation of single event effects in electronics
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050509
A collection of slides from the author's seminar presentation is given. (12 pages)The NSEU response of static-latch based FPGAs
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050511
A collection of slides from the author's conference presentation is given. (25 pages)Technical specification for atmospheric radiation single event effects (SEE) on avionics electronics
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050512
A collection of slides from the author's seminar presentation is given. (21 pages)A compact ultrafast capillary discharge for EUV projection lithography
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000273
Extreme ultra-violet lithography (EUVL) is expected to play an important role in the next generation of lithography system for the production of sub-100 nm feature microelectronic devices. An efficient source of EUV radiation in the 10-15 nm region has to be developed to comply with the demands for practical application. In this paper, the authors report on the development of a novel ultrafast hollow cathode triggered capillary discharge fitting with the desirable EUV region by operating in Xenon at low pressure. After being triggered by means of the hollow cathode effect ,the discharge starts on-axis. The resulting plasma channel is then heated up using a stored energy of less than 0.2 J before attaining the maximum temperature of 30 eV within a nanosecond timescale. During a pulse length of 5 ns concerning the EUV emission, the transient plasma inside the capillary whose aspect ratio is much more than 10 emits mainly between 10 and 20 nm, with a source size of less than 200 μm in diameter. The spectrum consists of Xe VII to Xe X line radiation. This very high energy efficiency allows practical scaling of the device to operate in the multi-kHz regime. (5 pages)Analysis of double-gate FinFET-based address decoder for radiation-induced single-event-transients
http://dl-live.theiet.org/content/journals/10.1049/iet-cds.2011.0253
In this study, the authors evaluate different schemes of address decoders based on bulk, single gate (SG) silicon-on-insulator (SOI) and double gate (DG) FinFET technology. Schemes differ in terms of back gate connections, and swing on the enable and address lines. The analysis for delay, power dissipation and critical charge has been carried out. Radiation induced single event transients and multiple bit upsets in address decoder have been studied. For radiation hardened applications, tied gate configuration has been found to be good choice over bulk, SG-SOI and independent gate configurations. The effect of process parameter variations on different schemes has been studied. HSPICE simulations have been performed with 45 nm bulk, SG-SOI and DG-FinFET predictive technology models.Analysis of the error susceptibility of a field programmable gate array-based image compressor through random event injection simulation
http://dl-live.theiet.org/content/journals/10.1049/iet-cdt.2011.0056
The successful use of commercial-off-the-shelf (COTS) devices on board space applications requires the use of fault mitigation methods because of the effects of space radiation in microelectronics devices. This study describes a scheme for the random injection of single event transients/upsets to evaluate the viability of employing COTS field programmable gate array for an onboard, low-complexity, remote-sensing image data compressor. The fault injection features are added to the application to be tested by modifying its hardware description language source code. Then the tests are executed by simulation, with or without the inclusion of fault mitigation methods, so that comparative evaluations can be quickly obtained. The evaluation results (robustness enhancement against area) of different fault mitigation methods are presented, with good estimates of the behaviour of the hardware implementation of the application in a space radiation environment.Radiation-induced changes in thin film structures
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20030664
Optical, electrical and structural properties of metal oxide thin films of tellurium dioxide (TeO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>), indium oxide (In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>) and silicon monoxide (SiO) and their mixtures were studied in terms of gamma radiation influence. These films were prepared using the thermal vacuum evaporation technique. <sup xmlns="http://pub2web.metastore.ingenta.com/ns/">60</sup>Co and <sup xmlns="http://pub2web.metastore.ingenta.com/ns/">137</sup>Cs sources were used to expose the samples to <i xmlns="http://pub2web.metastore.ingenta.com/ns/">γ</i>-radiation. It was found that the optical band gap values decreased with increasing radiation dose. The radiation induced changes in the electrical properties of these films. Devices with resistor-type structures and p-n junctions were studied. Irradiation resulted in the degradation of the device performance, e.g. current–voltage characteristics of these devices experienced significant alterations. It was observed that values of current were increased with increasing radiation dose. The response of these devices to radiation was found to be composition-dependent. Radiation-induced changes in the structure and surface morphology of In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>/SiO films were examined by scanning electron microscopy and X-ray diffraction. The irradiation of these thin films with a dose of 8160 μSv led to a change in their phase from amorphous to partially crystallised.Alpha-particle-induced effects in partially depleted silicon on insulator device: with and without body contact
http://dl-live.theiet.org/content/journals/10.1049/iet-cds.2010.0080
With the continuous downscaling of CMOS technologies, reliability has become one of the major bottlenecks in the evolution of next generation systems. The radiation-induced soft errors have become one of the most important and challenging failure mechanisms in the modern semi-conductor devices. The authors present an in-depth analysis of alpha-particle-induced effects in deep submicron partially depleted silicon on insulator (PD-SOI) device. Device with body contact as well as device without body contact is analysed. The process and device simulations are done with the latest models. Electrical parameter extraction under different energies of an alpha particle is carried out.Accurate and computer efficient modelling of single event transients in CMOS circuits
http://dl-live.theiet.org/content/journals/10.1049/iet-cds_20050210
A new analytical modelling approach to evaluate the impact of single event transients (SETs) on CMOS circuits has been developed. The model allows evaluation of transient pulse amplitude and width (duration) at the logic level, without the need to run circuit level (Spice-like) simulations. The SET mechanism in MOS circuits is normally investigated by Spice-like circuit simulation. The problem is that electrical simulation is time-consuming and must be performed for each different circuit topology, incident particle and track. The availability of a simple model at the logic gate level may greatly improve circuit sensitivity analysis. The electrical response of a circuit to an ionising particle hit depends on many parameters, such as circuit topology, circuit geometry and waveform shape of the charge injection mechanism. The proposed analytical model, which is accurate and computer efficient, captures these transistor-level effects of ionising particle hits and models them to the logic level of abstraction. The key idea is to exploit a model that allows the rapid determination of the sensitivity of any logic gate in a CMOS circuit, without the need to run circuit simulations. The model predicts whether or not a particle hit generates a SET, which may propagate to the next logic gate or memory element, making possible to analyse the sensitivity of each node in a complex circuit. Model derivation is strongly related to circuit electrical behaviour, being consistent with technology scaling. The model is suitable for integration into CAD tools, intending to make automated evaluation of circuit sensitivity to SET possible, as well as automated estimation of soft error rate.Effect of ionising radiation on the characteristics of a MOSFET
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20000203
The effect of radiation-induced changes on the characteristics of an <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-channel MOSFET has been investigated theoretically. A one-dimensional semi-numerical model of the device has been developed which can estimate fairly accurate characteristics of the device under unirradiated and irradiated conditions. The effect of ionising radiation on the channel voltage and electric field profile in the channel has been estimated numerically for the first time. The present model enables one to determine the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">I<sub>D</sub></i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">V<sub>D</sub></i> and transfer characteristics of the device by considering the field dependent mobility of the surface channel in the irradiated condition. The model presented here can be used as a basic tool for analysing MOS transistors exposed to a nuclear environment.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.Low-frequency noise and radiation response of buried oxides in SOI nMOS transistors
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20040432
The back channel low-frequency noise of 1.2 μm×2.3 μm SOI nMOS transistors with a buried oxide thickness of 170 nm was measured as a function of frequency, back gate bias <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>bg</i></sub> and temperature <i xmlns="http://pub2web.metastore.ingenta.com/ns/">T</i>. For a temperature range of 85≤<i xmlns="http://pub2web.metastore.ingenta.com/ns/">T</i>≤320 K, noise measurements were performed at frequencies of 0.3≤<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i>≤1 kHz with top gate bias <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>bg</i></sub>=0 V and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>bg</i></sub>−<i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>bg−th</i></sub>=4 V, where <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>bg</i>−<i>th</i></sub> is the back gate threshold voltage. The temperature and frequency dependences of the 1/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i> noise of back channel SOI nMOS transistors show thermally activated charge exchange between the Si channel and defects in the buried oxide. Comparison is made with the Dutta and Horn model of 1/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i> noise. Devices on one particular wafer appear to show a mixture of 1/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i> noise and noise with a higher frequency exponent at low temperatures. Little change is observed in back gate noise with irradiation for the devices and irradiation conditions studied. This is probably due to large preirradiation defect densities in the buried oxides.Electron irradiation effect on the Schottky gate of ZnO nanowires-based field effect transistors
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0229
The authors investigated the performance of ZnO nanowire-based metal–semiconductor field effect transistors (MESFETs) by focusing electron beam on the Schottky gate. The MESFET was fabricated by employing Tantalum as drain and source and by using Schottky barrier at tungsten–ZnO interface as the gate. As to <i xmlns="http://pub2web.metastore.ingenta.com/ns/">I</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DS</sub> against <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">GS</sub> curves, once the gate was illuminated with electron beam radiation, crests with a redshift as <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DS</sub> increased and a p-type semiconductor transistor behaviour were observed. At the critical points, the value of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DS</sub>−<i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">GS</sub> revealed a linear behaviour with the increasing <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DS</sub>. The authors attributed these results to the gain enhanced by electron beam radiation and carrier-trapping process, while the shift may be associated with the image-force lowing effect.High open-circuit voltage betavoltaic cell based on GaN <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> homojunction
http://dl-live.theiet.org/content/journals/10.1049/el.2011.1143
A high open-circuit voltage betavoltaic cell based on a GaN <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> homojunction is demonstrated. A process of doping compensation has been developed to achieve high resistance i-GaN film for betavoltaics. Under 0.5 mCi <sup xmlns="http://pub2web.metastore.ingenta.com/ns/">63</sup>Ni source irradiation, the open-circuit voltage of the fabricated GaN <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> homojunction betavoltaic cell was measured as high as 1.65 V. A fill factor of 54% and a 2.7% lower bound on the power conversion efficiency were obtained. The results suggest GaN is a highly potential candidate for the long-life betavoltaic cell.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.Reduction of U(VI) to U(IV) on the surface of TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> anatase nanotubes
http://dl-live.theiet.org/content/journals/10.1049/mnl_20080007
Titanium dioxide nanotubes were investigated as an adsorbent for the uranyl ion from solution under UV irradiation. Results from X-ray photoelectron spectroscopy analysis clearly indicate the reduction of U(VI) to U(IV) on the oxide surface.Reliability degradation of ultra-thin oxynitride and Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> gate dielectric films owing to heavy-ion irradiation
http://dl-live.theiet.org/content/journals/10.1049/el_20020119
The charge-to-breakdown of 3.3 nm oxynitride films shows significant degradation after irradiation with 342 MeV Au ions. In contrast, 5.4 nm Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> films exhibit much less degradation for similar heavy-ion stress.Defect dependent memory switching in amorphous silicon alloys
http://dl-live.theiet.org/content/journals/10.1049/el_20020160
It is shown that memory switching in amorphous silicon alloys is affected by ion bombardment. In particular, ion damage lowers the voltage required to form devices and switch them into the on-state. This technique enables optimised non-volatile memory devices to be made with improved switching ratios.Electrical properties of 1.55 µm sensitive ion-irradiated InGaAs with subpicosecond carrier lifetime
http://dl-live.theiet.org/content/journals/10.1049/el_20030441
Carrier lifetimes as short as 270 fs with carrier mobility of 200 cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>/V/s and good performances in terms of layer resistivity have been obtained from ion-irradiated InGaAs. The residual carrier concentration measured in Hall effect experiments was found to be weakly modified in spite of the high defect concentration created by the ion bombardment. Ion-irradiated InGaAs appears to be specially adapted to fast photoconductive devices operating at optical communication wavelengths.Irradiation induced weak spots in SiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> gate oxides of MOS devices observed with C-AFM
http://dl-live.theiet.org/content/journals/10.1049/el_20057289
A nanoscale characterisation of the electrical conduction of irradiated thin SiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> gate oxides of MOS devices has been performed with a conductive atomic force microscope. The electrical images reveal the existence of weak spots, which have been attributed to the electrical damage induced by irradiation. Although their <i xmlns="http://pub2web.metastore.ingenta.com/ns/">I</i>–<i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i> characteristics show a leaky behaviour, these locations have not experienced a hard breakdown event.Influence of trench-oxide depth on junction-size dependence of α-particle-induced charge collection
http://dl-live.theiet.org/content/journals/10.1049/el_20000802
The effect of trench-oxide depth on the α-particle-induced charge collection is analysed for various junction sizes. Simulation results indicate that the influence of trench-oxide depth on the charge collection substantially increases as the junction size is reduced. Confininement of the charge by the trench oxide in the reduced junction size is identified as a cause of this effect.Proposal for solid-state particle detector based on latchup effect
http://dl-live.theiet.org/content/journals/10.1049/el_20058364
A novel approach to detect particles by means of a solid-state device susceptible to latchup effects is described. The stimulated ignition of latchup effects caused by external radiation has so far proven to be a hidden hazard. This is proposed as a powerful means of achieving the precise detection and positioning of a broad range of particles with a spatial resolution of 5 µm.Optical sampling by ultra-fast high-contrast saturable absorber created by heavy ion irradiation
http://dl-live.theiet.org/content/journals/10.1049/el_19991066
A 4 ps high-sensitivity optical sampling scheme based on a fast GaAs saturable absorber created by heavy-ion irradiation is demonstrated. The intensity-invariant saturable absorber permits high-level inhomogeneous pumping leading to a high open/close ratio of 1000 and to a system sensitivity limited by the level of saturable absorber spontaneous emission.GaN-based SAW delay-line oscillator
http://dl-live.theiet.org/content/journals/10.1049/el_20010358
An SAW oscillator based on a GaN-sapphire acoustic delay line is reported. The oscillation frequency is determined by the GaN sound velocity and transducer period and is sensitive to temperature and to ultraviolet radiation. Our results show that GaN-based structures offer the possibility of integrating the acoustic and electronic elements on a single chip capable of operating at relatively high temperatures.Enhanced radiation hardness of quantum dot lasers to high energy proton irradiation
http://dl-live.theiet.org/content/journals/10.1049/el_20010118
The influence of high energy proton irradiation on the device properties of InGaAs/GaAs quantum dot and quantum well lasers has been investigated. In the regime of spontaneous emission, quantum dot lasers show a much enhanced radiation hardness compared to quantum well lasers, manifested in a smaller increase of threshold current density. However, in the lasing regime the device characteristics are similarly influenced. Internal differential quantum efficiencies are reduced, internal optical losses remain constant.RC hardened FPGA configuration SRAM cell design
http://dl-live.theiet.org/content/journals/10.1049/el_20040360
A radiation hardened configuration bit cell design is proposed for an SRAM-based FPGA used in space application. The <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-type gate poly on <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-substrate structure provides a radiation immune resistor and a capacitor for RC hardened signal path. In addition to area efficiency, the proposed cell also overcomes the traditional linear energy transfer sensitivity to process and temperature variation.DC electrical performance improvement of AlGaAs/InGaAs PHEMTs by using low thermal neutron radiation dose
http://dl-live.theiet.org/content/journals/10.1049/el.2010.0070
An original method is presented to improve DC electrical performance of AlGaAs/InGaAs PHEMTs by using a low neutron radiation dose. An increase of the drain–source saturation current, a decrease of the knee voltage and a reduction of the leakage current of the Schottky contact are observed without degrading the current-gain cutoff frequency when the devices are irradiated with a neutron radiation dose of 1.2×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">10</sup> neutrons/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>.Radiation hardening of power MOSFETs using electrical stress
http://dl-live.theiet.org/content/journals/10.1049/el_20020281
The effects of pre-irradiation gate bias stress on the radiation response of power VDMOSFETs are presented, clearly demonstrating the inapplicability of gate bias stressing as a technique for radiation hardening of power MOSFETs.High-speed AlGaN/GaN HFETs fabricated by wet etching mesa isolation
http://dl-live.theiet.org/content/journals/10.1049/el_20001351
The authors demonstrate high-performance AlGaN/GaN heterostructure field-effect transistors (HFETs) with mesa isolation achieved by a recently developed UV-assisted, batch processing compatible, wet etching process. HFETs with a 0.2 µm gate feature peak cutoff frequencies of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f<sub>T</sub></i> = 43 GHz and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f<sub>MAX</sub></i> = 98 GHz for a piezoelectric HFET grown on a sapphire substrate by molecular beam epitaxy. The transistors feature low gate diode leakage currents and display no sensitivity to visible light.Room-temperature self-annealing of heavy-ion-irradiated InGaAs/GaAs quantum wells
http://dl-live.theiet.org/content/journals/10.1049/el_20053117
The long-term stability of defects with the ageing of heavy-ion-irradiated and post-irradiated-annealed InGaAs/GaAs compound semiconductor quantum wells is reported using the time-resolved upconversion technique of luminescence lifetimes. The defects created by Ni<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup>-heavy-ion irradiation are found to be thermally unstable. The ageing tests prove that a substantial amount of defects are removed by self-annealing in about a month of time even at room temperature through a slow diffusion process, resulting in a dynamically stable sample but with a twofold increment in lifetimes. If the sample is annealed upon Ni<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">+</sup> irradiation, the defects are removed immediately, yielding stable and much longer relaxation times independent of the ageing process. These results may be useful in designing devices with an active region as ion-irradiated semiconductor quantum wells.Reduction of leakage current of 4H-SiC <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> diodes after UV light exposure
http://dl-live.theiet.org/content/journals/10.1049/el_20073494
A substantial reduction of the leakage current in 4H-SiC <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> diodes is observed after <10 eV UV irradiation in air. The high energy UV is believed to remove carbon clusters from the SiC surface. Comparison of leakage current in 4H-SiC <i xmlns="http://pub2web.metastore.ingenta.com/ns/">pin</i> diodes after different surface treatments, including reactive ion etching, exposure to two different sources of UV light and different forms of chemical cleaning, is presented. Exposure to 4.9 eV UV light in nitrogen atmosphere enhances the leakage by one order of magnitude.Wear-out and breakdown of ultra-thin gate oxides after irradiation
http://dl-live.theiet.org/content/journals/10.1049/el_20020757
The enhancement of gate leakage current after exposure to ionising radiation is generally believed to be the major challenge for devices and circuits operating in harsh radiation environments. How ultra-thin gate oxides subjected to heavy ion irradiation react to a subsequent electrical stress performed at low voltages has been investigated. Even in devices exhibiting small (or even negligible) enhancement of the leakage current, the time-to-breakdown is substantially reduced in comparison with unirradiated samples due to the onset of a soft or hard breakdown, in contrast with previous results found on thicker oxides.They come from outer space
http://dl-live.theiet.org/content/journals/10.1049/ir_20030805
Today, a system using hundreds of chips could suffer several soft error failures a month, and the problem is set to increase. Why is this and what are the implications?Neutron time bomb
http://dl-live.theiet.org/content/journals/10.1049/ess_20060605
Hardware errors and failures caused by radiation are becoming significant threats to a growing range of systems. Electronics manufacturers and the engineering industry have been investing more and more in research into single-event effects in recent years in order to determine the impact on system reliability today and in the future, but there is still much work to be done. For high-reliability applications, single-event effect consideration and mitigation at the design phase has become increasingly important, and with the continuing trends in technology miniaturisation, such considerations are likely to become more important in the future.Laser prototyping of MEMS structures and SiN cantilevers: experience teaching a practical undergraduate course
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_20040046
Bulk micromachining silicon to form microbeams is a common procedure in MEMS fabrication. A focused laser is used to cut patterns directly in a silicon nitride or silicon carbide mask layer to prototype new structures and test geometries. In the past two years this flexible approach has been used as the basis of a practical undergraduate course in which students (a) design shapes using CAD, (b) cut them using the laser system, (c) micromachine in a clean room using anisotropic wet etching, (d) take microscope images, and (e) use a mechanical profilometer to test the silicon nitride microbeams and measure the elastic modulus. This teaching approach is outlined and the utility of hands-on practical work in MEMS education is assessed.