ASSESSMENT OF SEMICONDUCTOR EPITAXIAL-GROWTH BY TRANSMISSION ELECTRON-MICROSCOPY

Defect microstructures within heteroepitaxial layers are categorized a ccording to whether they result from an inherent materials problem, ar e due to problems at the epilayer/substrate interface, ape introduced during growth itself or are formed during post-growth processing. Exam ples are presented which include dimorphism in CdS/GaAs, twinning in e pitaxial CdTe, interfacial misfit dislocation formation in ZnTe/GaAs, and interfacial phase formation in (Cd,Zn)S/GaAs. It is found that the development of (In,Ga)(As,P) based infrared multiple quantum well las ers grown by chemical beam epitaxy (CBE) is hindered by the limited co ntrol of the quaternary composition, as compared with gas source molec ular beam epitaxy material. The use of growth interrupts to characteri se gas switching procedures in CBE (ln,Ga)(As,P) is described. Relaxat ion initiation of molecular beam epitaxy SiGe/Si structures is associa ted with the presence of transition metal impurities. Surface profile imaging used to investigate the first stages of defect formation is de scribed with reference to the problem of microtwinning. (C) 1995 The I nstitute of Materials.