Growth and Characterization of Low Temperature InP by Gas Source MBE
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GROWTH AND CHARACTERIZATION OF LOW TEMPERATURE InP BY GAS SOURCE MBE G.N. MARACAS, K.T. SHIRALAGI, R.A. PUECHNER, F. YU, K.T. CHOI, J.S. BOW*, R. RAMAMURTI*, M.J. KIM* AND R.W. CARPENTER* Arizona State University, Dept. of Electrical Engineering, Center for Solid State Electronics Research, *Center for Solid State Sciences,Tempe, AZ 85287-5706 The introduction of GaAs grown at low MBE growth temperatures has spurred considerable activity in attempts to understand conduction mechanisms and optical properties. In LT GaAs, the formation of microscopic As precipitates dominates the conductivity, producing electronic transport mainly by variable range hopping conduction. The resulting high resistivity and short carrier lifetimes have enabled the use of LT GaAs in FET buffer layers as well as inultra-fast optical switches. An extension to AlInAs has also been performed and it was seen that variable range hopping is also present inthe Asbased ternary. We report the optical and electronic properties of InP grown at low temperatures in a gas source MBE using dimeric phosphorus produced from cracked phosphine. The conductivity is higher than the equivalent GaAs LT material and does not have the same temperature dependence. The conditions under which growth occurs ie, substrate temperatures, V/ill ratios and annealing is explored. The structural properties, temperature dependence of the conductivity, deep level structure and the photoluminescence properties of the material are also investigated. Introduction
The application of MBE GaAs grown at temperatures below 3000 C as an electrical buffer layer in field effect transistors [1] has spurred an investigation of other materials grown at low temperatures. Other material systems grown at low temperatures are AIGaAs [2] and InAlAs [3]. Several applications of low temperature (LT) materials have been developed in electronic and photonic devices. In this paper, we report the growth of InP at low temperatures by gas source MBE using sources of solid indium and P2. The dependence of electrical and optical measurements are explored as a function of growth temperature and V/ill ratio. The as-grown material properties are also measured as a function of anneal time and a correlation with phosphorus precipitates and ordered microcrystals observed by transmission electron microscopy (TEM) is made. Growth of LT InP Epitaxial layers were grown in a VG V80-H MBE system with solid indium and cracked phosphine. Two sets of samples were grown on semi insulating, Fe doped InP substrates for this study. The first and second sets had epitaxial layer thicknesses of 1.5 g±m and 0.3grm respectively. This was done to obtain material above and below the critical thickness for crystalline growth which is determined by the crystal strain induced by the excess P incorporated at low temperatures. Growth temperatures of 2400C, 2800C 0 and 320 C at a V/Ill atomic ratio of 1.150 were used for the growth temperature dependence study. Samples grown at 240 C at V/ill atomic ratios of 1.65, 1.50 and 1.25 were us
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