Volume 13, Issue 1-2
March 1990, pages 1-159
pp 1-2 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
pp 3-9 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
The growth of polycrystalline indium phosphide of different grain sizes varying from 15µm to 4000µm has been discussed. The materials have been characterized by a variety of methods including electrical and optical techniques. Device application of the InP prepared was demonstrated by the fabrication of Ag Schottky diodes andp+-n junction using Zn diffusion. The variation of mobility with varying grain size has been determined experimentally and the results interpreted taking into account the effect of compensation.
pp 11-26 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
In this paper, we shall review important aspects of the growth of thin single crystal layers of binary, ternary and quaternary III–V compound semiconductors by liquid phase epitaxy (LPE). The emphasis will be on materials which can be grown lattice-matched to the common substrate materials GaAs, InP and GaSb. Usefulness and limitations of the LPE technique are highlighted.
pp 27-32 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Gallium antimonide crystals were grown by the vertical Bridgman technique. Effects of ampoule diameter and dopant impurities (Te, P and In) on growth were studied. Crystal stoichiometry and homogeneity were verified with electron-probe microanalysis. Impurity distribution was investigated by secondary ion mass spectrometry (SIMS) and electron probe micro analysis. Variations of etch pit density (EPD) along the length and the diameter were studied by image analysis method. Resistivity, mobility and carrier concentrations were measured along the length of the crystal.
pp 33-36 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Liquid phase epitaxial growth of lattice-matched In0·53Ga0·47As layers on InP substrates is investigated with particular emphasis on the role of interface defects on layer quality. By differential Hall measurements it is established that a bad interface, resulting from the thermal decomposition of InP substrate prior to growth, degrade the electron mobility in all parts of the layer and the effect is most pronounced at regions close to the interface. However layers with much better physical and electrical characteristics are grown following steps to ensure substrate surfaces free from any thermal damage.
pp 37-41 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Use of rare earth (RE) elements has allowed the growth of high purity InGaAsP:InP layers in liquid phase epitaxial (LPE) systems. Experiments show that purification of material takes place on account of interaction between the RE and mainly group VI donor impurities.
pp 43-49 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
A kinetic model has been developed for the electrodeposition of GaAs from solution containing reducible ions of both constituents and is based on the generalised Butler-Volmer equation. The effect of hydrogen ion concentration and activities of ions on the total current density is studied. Voltammograms corresponding to various values of hydrogen ion concentration and activities of ions are constructed by the computer simulation technique.
pp 51-56 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
The progress in the area of applications of ion implantation and laser treatment to III–V semiconductors is reviewed. The achievements till todate are discussed alongwith the yet unresolved problems.
pp 57-63 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Monte Carlo results on the hot-electron transport coefficients of In(0·53) Ga (0·47) As are presented. The material parameters were selected by analysing the experimental hot-electron velocity-field characteristics and calculations were made by including all the relevant scattering mechanisms. Results are presented for the bulk drift velocity and diffusion coefficient and also for the velocity-field characteristics of submicron samples and 2 DEG.
pp 65-74 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Conditions for the formation of low-dimensional electron gas in semiconductors and different structures supporting it are discussed. Some of the new devices in which carriers have low-dimensional motion are introduced. The properties of electrons needed to be studied for the optimisation of the device performance are mentioned. In particular, the charge control and mobility of electrons in high electron mobility transistors, gain and loss processes in quantum well lasers, and excitonic line width in multiple quantum wells are discussed.
pp 75-82 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Photoluminescence (PL) studies on LPE-grown InP layers doped with selenium and having carrier concentrations from 1 × 1018 to 1 × 1020 cm−3 have been reported in this paper. Measurements at 300 and 77 K showed that the band to band recombination peak energy shifts to values as high as 1·7 eV with increasing doping, the increase being sharp beyond 4 × 1019 cm−3. These results have been explained as being the result of the Burstein shift and the band-gap shrinkage.
pp 83-88 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
It is well-known that the properties of semiconductor materials including gallium arsenide are controlled by defects and impurities. The characterization of these defects is important not only for better understanding of the solid state phenomena but also for improved reliability and performance of electronic devices. We have been investigating the defects in gallium arsenide for several years using deep level transient spectroscopy, photoconductivity, transient photoconductivity, photoluminescence etc. Results drawn from our recent studies are presented here to illustrate some of the problems concerning transition metal impurities, process-induced defects, occurrence of intracentre transitions and metastability of deep levels in gallium arsenide.
pp 89-94 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Single crystals of GaP and InSb were irradiated by 3 MeV electrons at 20 K to a total dose of 4 × 1018e−/cm2. Isochronal annealing in the temperature region 77–650 K followed the irradiation. In GaP, the positron lifetime measurement indicated the presence of irradiation-induced vacancies in the Ga-sublattice. The vacancies disappeared at two stages observed in temperature ranges 200–300 and 450–550 K. In InSb the positron lifetime was found to increase by 8 ps compared to that in as-grown crystals (i.e. 282±2 ps) after irradiation. The increase indicated the presence of irradiation-induced defects; the crystal was found to recover until 350 K with a sharp annealing stage at 250–350 K.
pp 95-98 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Formation of a uniformn-layer by multiple29Si+ implantation on LEC grown semi-insulating GaAs 〈100〉 substrate and its characterisation by differential Hall measurement at room temperature is reported. The implantation energies are 60, 160 and 260 keV with corresponding doses of 1 × 1012, 2·55 × 1012 and 3 × 1012 cm−2. Asimplanted, uncapped substrates were furnace-annealed with face-to-face configuration in an N2 ambient at 850°C with arsenic overpressure. After annealing, the samples were subjected to Hall measurements using Van der Pauw configuration. Experimental and theoretical (LSS) profiles are compared. Electrical activation of the dopant atoms was found to range from 65–90% with average mobility values lying between 2000–2300 cm2 V−1 s−1. Uniform concentration of then-layer ∼ 1017 cm−3 up to a depth of 0·3 µm has been achieved. These layers are used for the fabrication of power MESFETs.
pp 99-112 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Since inception of GaAs MESFET in 1971, growth and processing technology of GaAs has matured to the extent that the analogue as well as digital IC production is persued at the industrial level. The ever increasing demand for higher frequency of operation, low noise figure and higher gain has led to newer device structures such as HEMT and HJBT based on GaAs and related compounds. Furthermore there exists exciting and proven capabilities in GaAs and related compounds to generate, detect and convert light into electrical signals. This has opened up vast field of opto-electronic devices and their integration with MESFET and other conventional devices.
Basic building block of all these developmental activities still remains the GaAs MESFET, which have also been extensively used as low noise amplifiers, mixers, oscillators and high power amplifiers in descrete form. This paper reviews the design aspects, fabrication technology, d.c. and microwave characterization for both low noise and high power MESFET.
Various technological advancements like via-hole for source grounding, air-bridge technology for low parasitic interconnects and polymide passivation, which have helped in further improvement in terms of higher frequency of operation, low noise and high power output are reviewed.
Finally some representative results on the devices fabricated at CEERI are also presented.
pp 113-119 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
The static and high frequency properties of GaAs and InP impatts have been investigated for lower microwave and higher millimetre-wave frequencies using the computer simulation programmes developed by the authors. The profiles of negative resistance and reactance in the depletion layer of SDR and DDR devices based on GaAs and InP and their admittance properties have been investigated. The results indicate that InP impatts of the SDR and DDR varieties have higher drift zone voltage, higher negative resistance and higher negative conductance as compared to their GaAs counterparts, both in the microwave frequency and in the millimetre-wave frequency ranges. It is thus observed that higher radio-frequency power can be obtained from InP devices than from GaAs devices.
pp 121-133 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
In this article, I briefly review the physics of the high electron mobility transistor (HEMT), the technological steps involved in the fabrication of the device, the current status, the remaining problems, and some areas of active research in which new developments might be expected in the future.
pp 135-150 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
The motivations behind the development of GaAs integrated circuits (IC) are two-fold: to integrate high speed logic with optical sources and to meet the increasing demand of realising LSI/VLSI with higher speed and lower power dissipation for large scale computer applications. GaAs gigabit circuits have been growing in complexity to more than 3000 gates on a single chip. Although this is encouraging, more efforts are needed to improve production yield. By far the most work on GaAs digital IC has been done using MESFET as the active devices. MOSFET technology is yet to mature from the practical IC point of view. The logic gate types used in circuits are predominantly of the enhancement-mode driver and depletion-mode load configuration (E/D).
A brief survey of the state-of-the-art of GaAs digital IC is presented. Implemented circuits are described and compared with those achieved through various technologies. GaAs gate arrays, multipliers, accumulators and memories are discussed. At liquid N2-temperature, a switching time of 5·8 ps/gate has been achieved for 0·35µm gate devices. This and similar other results lead to the conclusion that at the VLSI level of future Gbit circuits, GaAs devices in the form of HEMT operated at 77 K can outperform Si-devices. At′ LSI complexities, experimental GaAs MESFET and 300 K HEMT have a lead on Sicircuits—it is then this range in which Gbit/GaAs should find their application.
pp 151-159 March 1990 First National Seminar On GaAs And III–V Compound Semiconductors
Recent progress in the development of semiconductor lasers for optical-fibre communication is reviewed. GaInAsP buried heterostructure and distributed feedback structure, are described in some detail. An overview of the novel GaInAsSb mid-infrared (2–4 microns) lasers is also presented.
Volume 42 | Issue 5
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