Phase identification and defect structures in II-IV-V2 heteroepitaxial semiconductor thin films grown on III-V substrates

Abstract

The ternary chalcopyrite-structure compound semiconductors (space group , Fig. 1) offer several promising materials properties that may be useful in electronic and optoelectronic devices. These compounds have a wide range of direct and pseudodirect band gaps, and they generally lattice match well to available substrates for heteroepitaxial growth. However, before the properties of this class of materials can be fully exploited, specific issues pertaining to the crystal growth (both bulk and epitaxial) must be understood and optimized. This contribution briefly describes some of our microstructural studies of heteroepitaxial ZnGeAs2-on-GaAs(100) and ZnGeP2-on-GaP(100) grown by organometallic chemical vapor deposition (OMCVD).The details of OMCVD growth of these materials are described in detail elsewhere. Cross-section [110] samples for transmission electron microscopy (TEM) were held at reduced temperature using a liquid nitrogen cooled stage to minimize the deleterious effects of Ar+ ion bombardment during final thinning. Diffraction contrast and phase contrast (HRTEM) imaging was accomplished at 200 kV.