MISFIT DISLOCATIONS IN EPITAXIAL ZNTE/GAAS (001) STUDIED BY HRTEM

Single-crystalline ZnTe epilayers were grown by atmospheric-pressure metal organic vapor phase epitaxy (MOVPE) and hot wall epitaxy (HWE) on (001) GaAs. The misfit of lattice constants is - 7.5% at the growth temperature of 350-degrees-C. Conventional transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) have been used to investigate the misfit dislocations in the ZnTe/GaAs (001) system. The types and distribution of the observed dislocations are independent of growth techniques used. The most common line defects at the ZnTe/GaAs interface are 60-degrees and Lomer dislocations with Burgers vectors of 1/2a[110]. Their respective abundance ratio 2:1. Less than 3% of the 60-degrees dislocations dissociate into partial dislocations limiting a stacking fault. The distances between parallel {111} planes terminating at the interface have been determined from an analysis of about 1 mum of the projected ZnTe/GaAs interface. The distribution fits by a Gaussian with an average distance of 57 angstrom. This allows an estimate of the residual biaxial strain at the interface which is found to be compressive with a magnitude less than 0.6%. The distances of the observed dislocation cores form a histogram. Its special shape shows four maxima at about 0, 5, 9 and 12 x 1/2a(s)[110]. They can be explained by a model for the correlated nucleation of misfit dislocations in highly mismatched heterostructures like ZnTe/GaAs.