Molecular Beam Epitaxial Growth and Electronic Properties of GaP-on-Si (211)Heterostructures, and of Related Systems

摘要

Two fundamental problems involved in the hetero-epitaxial growth of GaAs onsubstrates were investigated: a) The mechanism by which antiphase domain disorder is self-eliminating under proper growth conditions. b) The minimization of misfit-induced threading dislocations, and the properties of those dislocations that remain, especially their interactions with superlattice buffer layers. Although the self-elimination of antiphase domain disorder under proper growth conditions is experimentally beyond the shadow of a doubt, no truly satisfactory explanation for this phenomenon has been found. We propose that the self-elimination is of kinetic rather than energetic origin, and that the details of the annihilation mechanism depend sensitively on details in the kinetics. Superlattice buffer layers are only marginally effective in reducing threading dislocation densities of the magnitude occuring in GaAs-on-Si growth, and they are unable to reduce the densities to anywhere near the levels desirable for the more demanding device applications, such as lasers. A truly satisfactory level of dislocation reduction will probably require island-like growth on patterned substrates. Threading dislocations interact strongly with superlattice. The effect was traced to a reduction in the mobility of the minority carrier along the superlattice wells, presumably caused by dislocation-induced well width fluctuations. this causes the minority carriers to be effectively trapped in regions of enhanced well width, where they recombine radiatively before reaching he dislocation.