Material properties and performance of metamorphic optoelectronic integrated circuits grown by molecular beam epitaxy on GaAs substratesA technique for the heteroepitaxy of GaAs/Si films having reduced threading dislocation density is presented. The important attribute of this technique is the suppression of three-dimensional Volmer-Weber island formation during initial deposition. This suppression is achieved by deposition of a stoichiometric GaAs buffer layer by a migration-enhanced epitaxy technique on silicon at 348 K to a thickness greater than the ''monolithic thickness,'' h m . Subsequent GaAs films deposited by conventional molecular beam epitaxy on buffer layers of thickness greater than h m possess structural and optical characteristics that exceed those for state-of-the-art GaAs/Si layers: an x-ray full width at half maximum ͑FWHM͒ of 110 arcsec with a dislocation density at the film surface of 3ϫ10 6 cm Ϫ2 and a concomitant 4 K photoluminescence FWHM of 2.1 meV. The p-i-n structures suitable for use as light-emitting diodes ͑LEDs͒ that were grown on the reduced threading dislocation density GaAs/Si and by means of forward-and reverse-bias measurements, demonstrated an ideality factor of nϭ1.5, an increased reverse-bias breakdown electric field of 2.1ϫ10 7 V/m, and an intrinsic region resistivity of 4ϫ10 7 ⍀ cm for LEDs of increasingly smaller mesa size.
Widths of double-crystal x-ray rocking curves for epitaxial layers of the ternary alloy ZnCdTe are found to correlate with lattice parameter misfit between layer and substrate. Estimates of dislocation density in the layers are made using these widths. Values thus obtained are found to be in good agreement with values reported for other materials with similar misfit.
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