Defects in Large-Misfit Heteroepitaxy

Abstract

AbstractA Transmission Electron Microscopy (TEM) study is presented of GaAs on Si (100) and CdTe on GaAs (100), and the implications for defect nucleation mechanisms are discussed. MOCVD GaAs/Si is shown to grow by island nucleation followed by 3D growth. Single islands are free of inversion domain boundaries (or “APBs”) implying that a single domain is able to grow over a demi-step on the substrate surface during this 3D growth. Misfit dislocations are shown to be edge type during island growth, with 60° type being generated at island junctions. The predominant threading dislocations are found to have inclined a/2 <110> Burgers vectors. The implied mechanisms for the generation of both misfit and threading dislocations are discussed. In MOCVD CdTe/GaAs the microstructure is shown to have a number of qualitatively similar features; in addition, study of this much larger misfit system allows us to deduce a possible explanation for misorientation effects in these systems.