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Comparison of GaAs Heteroepitaxy on Si and InP Substrates

24 April 1989

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The heteroepitaxy of GaAs on foreign substrates is of great interest because of its potential for novel monolithic optoelectronic integrated circuits; e.g., the integration of GaAs optical devices with high-density silicon IC technology for GaAs on Si and, conversely, the combination of high-speed GaAs electronics with long wavelength InP-based optical devices for GaAs on InP. However, a high number of misfit dislocations (>10 sup 7 cm sup (-2)) and large internal stresses (,10 sup 9 dynes/cm sup 2) are present in the heteroepitaxial films due to the lattice (3.7-4%) and thermal (22-56%) mismatches between the epilayer and substrate materials. These greatly affect the structural, optical and electrical properties of the films. We report a comparison of these effects in MOCVD-grown GaAs/Si and GaAs/InP using X-ray diffraction, photoluminescence (PL) spectroscopy and carrier concentration measurements. The X-ray rocking curve data indicate that the quality of the heteroepitaxial layers improves with film thickness, with measured linewidth (FWHM) of approximately 200 arc-s being attained for 4.0micron films on both the Si and InP substrates. The magnitude of the film strain was determined from both the X-ray and PL measurements and was found to be consistent with the thermal expansion mismatch of the respective substates. Patterned GaAs growth on Si and InP substrates was also investigated, and its effect on the film strain field and dislocation densities will be discussed.