Molecular-Beam Epitaxial Growth and Device Potential of Polar/Nonpolar Semiconductor Heterostructures

摘要

Techniques for the molecular beam epitaxial growth of GaP and GaAs on substrates were developed. The techniques rely on the total in-situ removal of all oxygen from the Si surface, to create an atomically clean Si starting surface, coupled with the use of the unusual and previously not used crystallographic (211) orientation for the Si substrate. In the case fo GaP growth a third essential ingredient was the use of pure P2 vapor, generated by the high-temperature decomposition of GaP, rather than the P4 vapor generated by the evaporation of elemental phosphorus. The central problem of obtaining device-quality growth of GaAs and GaP was found to be the problem of avoiding antiphase domains (APDs) in the growing film, that is, of random domains containing opposite assignments of the lattice positions to the Ga and P atoms. On the commonly used crystallographic (100) orientation, APDs are fundamentally unavoidable. The (211) orientation was recognized to have a bond configuration at the interface such that APDs should not form. Experimental (211) growths yielded layers of high quality that were demonstrably free of APDs, as predicted. The recognition of the (211) orientation as the canonical orientation for the growth of polar compound semiconductors on non-polar elemental semiconductor substrates was a completely unexpected result of this research, and perhaps the most far-reaching one.