Photoelectronic Properties of Low Temperature GaAs Grown on Silicon and GaAs Substrates by Mbe
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PHOTOELECTRONIC PROPERTIES OF LOW TEMPERATURE GaAs GROWN ON SILICON AND GaAs SUBSTRATES BY MBE
RAYMOND P. MARIELLA*, JEFFREY D. MORSE*, ROGER AINES* AND CHARLES E. HUNT** *Lawrence Livermore National Laboratory, P. 0. Box 808, Livermore, CA 94550 ** Department of Electrical Engineering, University of California, Davis, CA
ABSTRACT The characteristics of GaAs layers grown by MBE at growth temperatures from 2000C to 4000 C have been evaluated by photoconductivity experiments in order to understand the photoelectronic properties of this material. Low temperature (LT) growth of GaAs on both silicon and GaAs substrates has been investigated in an attempt to better understand the nature of defects which are created in epitaxial layers grown under these conditions. Results from experiments on both annealed and unannealed LT samples indicate that the electronic transport properties of the epilayers can be controlled by selecting the appropriate growth conditions.
INTRODUCTION Growth of GaAs epitaxial layers on both GaAs and silicon substrates by MBE at reduced substrate temperatures has proven an effective means for obtaining several material properties desireable for both GaAs and silicon integrated circuit technology. By growing the GaAs at substrate temperatures ranging from 200*C-400*C, significantly lower than the normal growth temperature of 600'C, with Ga and As 4 beam fluxes under arsenic stable conditions, the LT epitaxial layer maintains a large concentration of ASGa type defects [1] which behave as deep level trapping centers to compensate the slightly n-type doped material, providing an insulating crystalline epilayer which has proven effective in reducing or eliminating backgating effects in GaAs MESFET circuits , increased the drain resistance and backgate voltage holdoff capability substantially for recessed gate MESFET structures [2]. Furthermore, this material is an excellent material for picosecond photoconductors, maintaining a comparatively high mobility for materials exhibiting picosecond recombination lifetimes [3,4]. Therefore, obtaining further insight into the nature of both point defects and structurally related defects relative to the growth conditions and pre/post-processing steps, this technology undoubtedly will have a significant impact on silicon, GaAs and optoelectronic integrated circuit technology.
ANALYSIS USING PICOSECOND PHOTOCONDUCTIVITY Since the application of interest is high speed photodetectors and picosecond electrical sampling, experiments utilizing picosecond optical pulses have been conducted to characterize the transport properties of LT GaAs grown on SI GaAs and silicon substrates. These results provide a better understanding of the deep level defects which are created by growing epitaxial GaAs under such conditions, allowing a direct evaluation of the photocurrent transient response corresponding to the particular growth conditions and annealing cycle for the epitaxial layers. Mat. Res. Soc. Symp. Proc. Vol. 145. ©1989 Materials Research Society
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