Low-Temperature Growth and Characterization of InP Grown by Gas-Source Molecular-Beam Epitaxy
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LOW-TEMPERATURE GROWTH AND CHARACTERIZATION OF InP GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY B. W. Liang, Y. He and C. W. Tu Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093-0407.
ABSTRACT Low-temperature (LT) growth of InP by gas-source molecular-beam epitaxy has been studied. Contrary to GaAs, InP grown at low temperature (from 200 'C to 410 0 C) shows ntype, low-resistivity properties. The electron concentration changes dramatically with growth temperature. A model of P antisite defects formed during LT growth was used to explain this experimental result. Ex-situ annealing can increase the resistivity, but only by a factor of about 6. Heavily Be-doped LT InP also shows n-type property. We believe this is the first report of an extremely high concentration of donors formed in LT InP and n-type doping by Be in III-V compounds.
INTRODUCTION
Annealed GaAs layers grown at low temperature exhibit extremely high resistivity [1-3] and short carrier lifetime [4, 51, but unexpectedly high mobility [4]. High resistivity is desirable for both field-effect transistors and optoelectronic devices. Short carrier lifetime combined with high mobility, is advantageous for ultra-fast switches. Low-temperature growth of various arsenides has become one of the most interesting topics today. Different models have been proposed to explain the properties of LT GaAs [6,7]. As another important member of the rn1-V family, InP grown at low temperature and its properties have not been investigated. In this paper, we have systematically studied the growth of InP by gas-source molecular-beam epitaxy (GSMBE) at low temperature (from 200*C to 410'C), and the properties of both as-grown and annealed LT InP thin films by reflection high-energy electron diffraction (RHEED), Hall-effect measurement, I-V characteristics, and photoluminecence. Extremly high concentration of donors and anomalous doping behavior of Be in LT InP grown by GSMBE has been observed for the first time.
EXPERIMENTAL PROCEDURE The samples were grown in an Intervac (Varian) Gen-II MBE machine modified to handle arsine and phosphine. An Intervac gas cracker for cracking group-V hydrides and EPI Mat. Res. Soc. Symp. Proc. Vol. 241. (c01992 Materials Research Society
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effusion cells for In, Ga, Be and Al were used. The growth rate of InP was fixed at 1 monolayer per second. The growth temperature was calibrated by a pyrometer and the melting point of
InSb. The cracker temperature was 1000°C. The LT InP layers were grown in the growth temperature range of 2000 C to 410 0 C, and with a phosphine flow rate range of 0.8 sccm to 2.4 sccm. Ex-situ annealing was performed in forming gas (15% H 2 and 85% N2 ). During proximity annealing, the sample surface was protected by another piece of InP substrate.
RHEED pattern was used to monitor the growth front. Hall-effect measurements and I-V curves were used to characterize electrical properties of LT InP grown on (001) semi-insulating and n+InP substrates, respectively. P
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