Plasma-Assisted Epitaxial Growth of Compound Semiconductors for Infrared Application
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PLASMA-ASSISTED EPITAXIAL GROWTH OF COMPOUND SEMICONDUCTORS FOR INFRARED APPLICATION K. MATSUSHITA,
T. HARIU,
Department of Electronic Sendai 980, Japan
S. F. FANG, K. SHIDA AND Q. Z. GAO Engineering,
Tohoku University,
ABSTRACT GaSb, InSb and InAs epitaxial layers with mirror surface were grown on GaSb, GaAs, InP, Si and sapphire substrates at relatively low temperatures by plasma-assisted epitaxy (PAE) in hydrogen plasma. Carrier concentrations and Hall mobilities of undoped PAE layers at room temperature are p=6xO16 cm'3; •p=750cm2/Vs, n~lx1016cm3; j•n=39,000cm2/Vs and n=7xl017cm'3 jjn=21,00Ocm2/Vs
for GaSb on GaAs,
InSb on GaAs and InAs on InP,
respectively. As the first application of PAE layers to optoelectronic devices, p-GaSb/n-GaAs heterojunction photodiodes have been demonstrated to result in remarkable reduction of dark current with photoresponse in the wavelength region between 0.85 and 1.7jim for the light incident from GaAs.
INTRODUCTION GaSb, InSb, InAs and their alloys are attractive materials for application to optoelectronic devices in the longest wavelength infrared region of all III-V compound semiconductors. These devices can be discrete, as some of them have already been in practical application, but they are desired to be integrated on the same chip of Si IC or higher speed GaAs IC to achieve more intelligent functions with higher sensitivity and higher speed. It is then required to develop technologies which can grow these materials epitaxially at low temperatures even on lattice mis-matched substrates, as in the case of GaAs on Si which recently has been extensively investigated. The purpose of this paper is to describe first the growth behaviors and the electronic properties of plasma-assisted epitaxial GaSb, InSb and InAs layers on different substrates, and second the electrical characteristics and photoresponse of p-GaSh/n-GaAs heterojunction photodiodes which are fabricated by PAE GaSb layers directly grown on n-GaAs substrates.
PLASMA-ASSISTED
EPITAXY
(PAE)
PAE has been developed for the low temperature epitaxial growth of semiconductor crystals by supplying atoms with enhanced internal energy to activate chemical reaction and kinetic energy for migration on the growing surface [1]. Several other advantages of PAE, including the cleaning effect of substrate surface at low temperatures have already been confirmed 12,3]. Similar PAE apparatuses as described elsewhere [4,51 were used for the growth of GaSb, InSb and InAs layers. In order to precisely control the supply rate of constituent atoms independent of plasma conditions, elemental sources (6-nine purity) were used and supplied from resistively heated crucibles, in the same way as MBE. through hydrogen plasma to substrates. The use of hydrogen gas at 10-I- 10-2Tort was found to give epitaxial layers of much better quality compared with other plasma gases. Different substrates including GaSh, GaAs, InP, Si and sapphire were used to compare the relaxation of lattice mis-match and the electronic properties of grown layers.
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