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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 25, Issue 24, 23 November 1989

Volumes & issues:

Volume 25, Issue 24

23 November 1989

Damage-free reactive ion etching of GaAs FET gate recess
Abrupt p+ layers in GaAs by 200°C mercury implantation
  • Author(s): A.C.T. Tang ; S.R. Gardner ; B.J. Sealy ; W.P. Gillin
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1618 –1620
  • DOI:  10.1049/el:19891084
  • Type: Article
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  • p. 1618 –1620 (3)
    We have demonstrated for the first time abrupt and shallow p-type layers in GaAs by implanting mercury and the use of rapid thermal annealing (RTA). We have observed that the time dependence of electrical activation characteristics of the Hg-implanted samples is similar to other p-type species. Furthermore, abrupt electrical profiles with hole concentrations of the order of 9×1018cm−3 have been achieved after annealing at 900°C for 3 s.
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Electric decoupling of reverse-biased optical DH modulators using delta doping
GaInAs/GaInAsP multiple-quantum-well integrated heterodyne receiver
  • Author(s): T.L. Koch ; U. Koren ; R.P. Gnall ; F.S. Choa ; F. Hernandez-Gil† ; C.A. Burrus ; M.G. Young ; M. Oron ; B.I. Miller
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1621 –1623
  • DOI:  10.1049/el:19891086
  • Type: Article
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  • p. 1621 –1623 (3)
    We describe the fabrication and performance of the first integrated heterodyne receiver capable of actual heterodyne data reception. Integrating a continuously tunable 1.5 μm MQW-DBR laser with a single-mode directional coupler/switch and zero-bias MQW waveguide photodetectors, we have achieved error-free reception of FSK-modulated pseudorandom digital code at 105 Mbit/s.
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Experimental determination of carrier-induced differential loss in 2-section GaInAsP/InP laser-waveguide
  • Author(s): P. Brosson ; C. Labourie ; L. Le Gouezigou ; J.L. Lievin ; J. Jacquet ; F. Leblond ; A. Olivier ; D. Leclerc
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1623 –1624
  • DOI:  10.1049/el:19891087
  • Type: Article
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  • p. 1623 –1624 (2)
    Measurements of threshold crrent density and external efficiency on broad-area laser-waveguide structure have led to the determination of the optical loss and differential loss dα/dN ≃1.1–2.3 × 10−17cm2 at λ = 1.53μm in a λg 1.30μm GaInAsP layer. This measurement will be useful for the design of tunable lasers.
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Proof of polarisation independence and nonexistence of crosspolar terms for targets presenting n-fold (n>2) rotational symmetry with special reference to frequency-selective surfaces
Role of coupling fluid in acoustic signature V(z)
  • Author(s): J. Attal ; C. Amaudric Du Chaffaut ; K. Alami ; H. Coelho-Mandes ; A. Saied
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1625 –1626
  • DOI:  10.1049/el:19891089
  • Type: Article
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  • p. 1625 –1626 (2)
    The acoustic material signature (AMS), also called V(z), constitutes a unique function that arises from interference of elastic propagating modes in the reflective acoustic microscope. More than only Rayleigh modes can participate in the AMS, and we show that by choosing an appropriate coupling fluid, such as mercury, longitudinal modes can also be generated with high efficiency conversion.
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Frequency stabilisation of FDM optical signals by time division multiplexing
Performance of LAN token passing protocol under asymmetric traffic loads
Using FHT to determine digital straight line chain codes
GaAs heterostructure FET frequency dividers fabricated with high-yield 0.5/μm direct-write trilevel-gate-resist
  • Author(s): F. Ren ; D.J. Resnick ; D.K. Atwood ; C.W. Tu ; R.F. Kopf ; N.J. Shah
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1631 –1632
  • DOI:  10.1049/el:19891093
  • Type: Article
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  • p. 1631 –1632 (2)
    Frequency dividers and FET test structures have been fabricated on selectively doped n+-AlGaAs/GaAs heterostructure FETs (HFETs) with 0.5 μm gate length electron-beam direct writing on a novel trilevel resist, EBR-9/Ge/PMGI. A divide-by-two master-slave frequency divider fabricated with direct-coupled FET logic gates operated up to 9.3 GHz. The input frequency range of a divide-by-two transmission-gate frequency divider was from 3.2 to 12.2 GHz, with a supply voltage of 1.2 V at room temperature. The average propagation delay (fan-in and fan-out = 1) was 18.2ps/gate, with a power dissipation of 3.9 mW/stage. With a 3.5 μm source-drain spacing, a peak transconductance of 360mS/mm was measured. The functional yield of both discrete devices and circuits was 92% across 2 in-diameter wafers.
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High-speed photodetector characterisation by delayed self-heterodyne method
Modal cutoffs in graded-core single-polarisation fibres
  • Author(s): Chen Zhihao
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1634 –1635
  • DOI:  10.1049/el:19891095
  • Type: Article
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  • p. 1634 –1635 (2)
    A graded-core single-polarisation fibre is proposed, and the dispersion equation for its modes is obtained. Very simple asymptotic formulas are derived giving the cutoff frequency as a function of K which determines the depth of the depressions of the cladding when K is small. By incorporating stress anisotropy, it is found that the absolute single-polarisation frequency bandwidth can be increased in the graded-core, stress-applied polarisation-maintaining fibres compared with the conventional step-index profile. The relative frequency bandwidth is approximately the same for the graded-core or step-index profiles.
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High-power 1.5μm all-MOVPE buried heterostructure graded index separate confinement multiple quantum well lasers
a-Si:H TFTs using low-temperature CVD of Si3H8
Experimental results of radio-frequency radiation measurements from cellular telephones
  • Author(s): G. Butt  and  M. Richharia
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1638 –1640
  • DOI:  10.1049/el:19891098
  • Type: Article
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  • p. 1638 –1640 (3)
    Measurement results of radio-frequency field strength from cellular telephones are reported. Transportable and handheld portable sets were used for the study, and their radiation levels were compared with the International Radiation Protection Agency (IRPA) and UK exposure standards as a function of distance for two operational environments. The hand-held portable set, which uses very low-power transmissions, was found to have radiation levels well within the prescribed limits. For the transportable radiophone, exposure levels are within limits for the UK standards, but are violated at certain points close to the antenna for IRPA standards. However, the position of the antenna in such telephones is well away from the user under normal operating conditions, where the radiation levels are well within limits.
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Analysis of drain breakdown voltage in SOI n-channel MOSFETs
  • Author(s): M. Haond  and  J.P. Colinge
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1640 –1641
  • DOI:  10.1049/el:19891099
  • Type: Article
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  • p. 1640 –1641 (2)
    The reduction of drain breakdown voltage in SOI n-MOSFETs with floating substrate is related to the presence of a parasitic NPN bipolar structure, the base of which is the floating body of the device. Reduction of breakdown voltage (compared to the case where a body contact is used) is shown to be dependent on both channel length and minority carrier lifetime in the SOI material. Conversely, it is shown that mere measurement of MOSFET breakdown voltages can be used to extract the minority carrier lifetime in the SOI material.
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Method of obtaining algorithms for nonblocking two-dimensional optical multistage interconnection networks
Pitch predictive vector quantisation of speech waveform
  • Author(s): A. Lowry  and  S.Q.A.M.A. Hossain
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1643 –1644
  • DOI:  10.1049/el:19891101
  • Type: Article
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  • p. 1643 –1644 (2)
    A coding algorithm is presented with low-dimensional vector quantisation to exploit both long- and short-term correlation in the speech waveform at rates of 16 and 9.6 kbit/s. Vector quantisation of the predictor enables the stability of the synthesis filter to be assured, and also allows the use of a minimum residual energy criterion. SNRs of 17–19dB are achieved at 16kbit/s and 13–15dBat9.6kbit/s.
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Use of implant isolation for fabrication of vertical cavity surface-emitting laser diodes
  • Author(s): K. Tai ; R.J. Fischer ; K.W. Wang ; S.N.G. Chu ; A.Y. Cho
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1644 –1645
  • DOI:  10.1049/el:19891102
  • Type: Article
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  • p. 1644 –1645 (2)
    We report the first successful use of implant isolation by singly charged oxygen to fabricate MBE-grown vertical cavity surface-emitting lasers (VCSELs). Almost identical room-temperature pulsed thresholds of 26 mA on 15μm diameter devices with 0.25μm GaAs active thicknesses were obtained using implant isolation against etched mesa isolation. The planar nature of implant isolation greatly simplifies processing, to allow more sophisticated use of VCSELs.
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Frequency domain measurements of indoor radio channels
  • Author(s): K. Pahlavan  and  S.J. Howard
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1645 –1647
  • DOI:  10.1049/el:19891103
  • Type: Article
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  • p. 1645 –1647 (3)
    Frequency responses of the indoor radio channel for 128 locations in an office and a research laboratory are analysed. Some statistics on the number of fades arc determined. The cumulative distribution function (CDF) of the 3dB bandwidth of the frequency correlation function is presented, and experimental results relating the RMS delay spread of the channel and the inverse of the 3dB width of the frequency correlation function are given.
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Realisation of 2D analogue filters
High-Q helical resonator for oscillators and filters in mobile communications systems
1.5 μm GaInAsP/InP distributed reflector (DR) laser with high-low reflection grating structure
  • Author(s): M. Aoki ; K. Komori ; Y. Miyamoto ; S. Arai ; Y. Suematsu
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1650 –1651
  • DOI:  10.1049/el:19891106
  • Type: Article
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  • p. 1650 –1651 (2)
    A 1.5 μm-wavelength dynamic-single-mode laser with highlow reflection grating structure aiming at high output and one-directional output operation has been obtained for the first time using a selective etching process and low-pressure MOVPE regrowth. A front/rear output power ratio exceeding 50 and side-mode suppression ratio (SMSR) greater than 39dB were obtained at 1.3 times the threshold.
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Feasibility study on common polarisation control for coherent FDM transmission system
High-speed InP/GaInAs photodiode on sapphire substrate
  • Author(s): H. Schumacher ; T.J. Gmitter ; H.P. Leblanc ; R. Bhat ; E. Yablonovitch ; M.A. Koza
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1653 –1654
  • DOI:  10.1049/el:19891108
  • Type: Article
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  • p. 1653 –1654 (2)
    Using epitaxial lift-off by selective wet-chemical etching, we have transferred an InP/GalnAs photodiode onto a sapphire substrate. The transferred diode shows an estimated 13.5 GHz bandwidth and 90% internal quantum efficiency. Our technique has promising applications in highperformance optoelectronic circuits for fibre-optic communications systems combining device from different material systems.
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New λ/4 phase-shift method by conversion of refractive index difference and application for 1.5 μm GaInAsP/InP DFB laser
  • Author(s): J.I. Shim ; K.S. Lee ; S. Arai ; Y. Suematsu ; K. Komori
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1654 –1656
  • DOI:  10.1049/el:19891109
  • Type: Article
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  • p. 1654 –1656 (3)
    A new method to introduce a phase shift of π/2 equivalently by inversion of the refractive index difference, which can be easily done by conventional photolithography, is proposed and applied for a 1.5 μm GalnAsP/lnP DFB laser. The λ/4 shifted effect was confirmed by observing the lasing spectrum of an antireflection-coated DFB laser below threshold under CW operation.
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46.5 dB gain in Er3+-doped fibre amplifier pumped by 1.48 μm GaInAsP laser diodes
Asymptotic surface field of slot antenna on coated cylindrical conductor
Periodic flux interruption and sustained two-dimensional growth for molecular beam epitaxy
Tunable CW lasing around 0.82, 1.48, 1.88 and 2.35 μm in thulium-doped fluorozirconate fibre
Efficient implementation of piecewise linear activation function for digital VLSI neural networks
Bit-serial modular multiplier
Lightwave CATV systems using frequency-modulated laser and interferometer
Two-dimensional analysis of microstrip resonator with dielectric protective layer radiating into human body
  • Author(s): J. Pribetich ; P. Kennis ; P. Pribetich
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1666 –1668
  • DOI:  10.1049/el:19891117
  • Type: Article
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  • p. 1666 –1668 (3)
    The originality of this letter is that previous modelling does not obtain the resonant frequencies of the rectangular microstrip resonator with a dielectric protective layer radiating into a human body (i.e. the resonant frequency Fr and the Q-factor). This analysis is based on the two-dimensional spectral domain approach (SDA). The comparison with experiment shows that the method improves on the previous one-dimensional model.
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Self-photo-induced phase modulation in GaAs/AlGaAs multiple quantum well waveguides
  • Author(s): C. Thirstrup ; P. Li Kam Wa ; M.A. Pate ; J.S. Roberts ; P.N. Robson
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1668 –1669
  • DOI:  10.1049/el:19891118
  • Type: Article
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  • p. 1668 –1669 (2)
    We report results of the nonlinear refractive index in GaAs/ AlGaAs pin diode multiple quantum well waveguides based on the quantum confined Stark shift of the exciton peaks due to a photon-induced change in the electric field. An increase in the nonlinearity can be obtained by connecting the waveguides to an external bias circuit with little or no speed penalty.
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Calculation of number of relay hops required in randomly located radio network
Worst month prediction model for transhorizon microwave interference
  • Author(s): M.T. Hewitt ; M.J. Mehler ; G.D. Bye ; U.O. Larsen ; A. Mawira ; J. Dijk
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1671 –1672
  • DOI:  10.1049/el:19891120
  • Type: Article
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  • p. 1671 –1672 (2)
    A model is developed to calculate the (average) worst month clear-air microwave interference statistics for land, sea and mixed land/sea paths. The model predicts the parameter Q, which relates the worst month statistics to the average annual statistics, derived either by measurementsor by prediction. By providing a reliable means of computing worst month statistics, the model addresses a major deficiency in the existing CCIR interference prediction procedures. The validity of the model is established by comparison with measured data from 1.3GHz transhorizon propagation experiments in northwest Europe.
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New approach for Doppler ambiguities resolution in medium pulse repetition frequency radars
New CMOS OTA for fully integrated continuous-time circuit applications
Partially doped GaAs single-quantum-well FET
  • Author(s): F. Ren ; C.W. Tu ; R.F. Kopf ; C.S. Wu ; A. Chandra ; S.J. Pearton
  • Source: Electronics Letters, Volume 25, Issue 24, p. 1675 –1677
  • DOI:  10.1049/el:19891123
  • Type: Article
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  • p. 1675 –1677 (3)
    We report on 1 μm gate length n+ AlGaAs/partially doped GaAs/n+ AlGaAs singie-quantum-well (PDSQW) FETs with a high extrinsic peak transconductance of 300 mS/mm. An acceptably high transconductance is maintained over 2.8 V gate-voltage swing. The FETs demonstrate a sharp pinch-off around Vg= −2 V, and a full channel current of 820 mA/mm was observed at room temperature. The PDSQW structures exhibit a two-dimensional electron-gas (2DEG) sheet charge density as high as 34 × 1012cm−2 with mobility of 17000cm2/Vs at 77 K. The PDSQW structure combines the advantages of both the conventional single-quantum-well (SQW) structure (high mobility and good carrier confinement) and the doped-channel structure (high carrier density).
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