InP Layers Grown by Molecular Beam Epitaxy at Low Substrate Temperature
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InP LAYERS GROWN BY MOLECULAR BEAM EPITAXY AT LOW SUBSTRATE TEMPERATURE K. Xie, and C. R. Wie State University of New York at Buffalo, Dept. of Electrical and Computer Engineering, Bonner Hall, Buffalo, NY 14260 G.W. Wicks Institute of Optics, University of Rochester, Rochester, NY 12627 ABSTRACT InP layers were grown on semi-insulating InP wafer by molecular beam epitaxy (MBE) at low substrate temperatures (< 2000 C), using solid phosphorus source. We use x-ray diffraction, double crystal x-ray rocking curve, Auger electron spectroscopy, and temperature-dependent Van der Pauw and Hall effect measurements to characterize the as-grown and annealed InP layers. It is found that the InP layer is in poly-crystal state with excess P over 7 at%. The layers became single crystal after annealing above 400'C. The resistivity of the InP layer decreased from 60 Ocm for an as-grown sample to 0.82 Kicm after 400'C RTA annealing. The different role of excess P as compared to the role played by excess As in LT-GaAs is discussed based on the P properties.
INTRODUCTION InP is an important compound semiconductor material for high speed electronic and optoelectronic devices. The sidegating and backgating problems associated with hnP based devices require a substrate with improved electrical properties. Recently, GaAs grown by molecular beam epitaxy (MBE) at low substrate temperature (LT-GaAs) has been shown to be a promising material [1]. The use of LT-GaAs as a buffer layer led to a great reduction of sidegating and backgating, and an increase in breakdown voltage in FETs [1, 2]. Successful growth of other As-based compounds such as AIGaAs and AllnAs have been reported, showing properties similar to LT-GaAs [3, 4]. Typical characteristics of these LT materials are (1) large amount of excess As (up to l-2at%), (2) high density of defects such as As precipitates and ASGa antisite defects, and (3) a relatively high crystalline quality. Further extension of low substrate temperature growth to lnP would be of great interest. Norris [5] had reported MBE growth of InP at various substrate temperatures. But he did not study the stoichiometry and annealing behavior of InP layer grown at low substrate temperatures (< 300'C). In this paper, we report the growth and materials characteristics of LT-InP. The growth is performed at different substrate temperatures and P over-pressures. Electrical and structural properties, and annealing behavior of these LT-InP layer are reported. Implications of our results are also discussed. InP GROWTH The Riber 32P MBE system with a valved, solid phosphorus source which has Mat. Res. Soc. Symp. Proc. Vol. 241. 01992 Materials Research Society
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been described previously [6] is used to grow the InP layer. Red phosphorus is used as the phosphorus beam source. The phosphorus source temperature was kept at 350'C with the temperature of the cracker zone kept at 1000°C. The P2 beam flux was controlled by varying its equivalent vapor pressure. Fe-doped semi-insulating (100) lnP wafers were used as substrates. Th
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