Misfit dislocations in epitaxial ZnTe/GaAs (001) studied by HRTEM

Abstract

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°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° and Lomer dislocations with Burgers vectors of 1 2 a〈110〉. Their respective abundance ratio is 2:1. Less than 3% of the 60° 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 μm of the projected ZnTe/GaAs interface. The distribution fits by a Gaussian with an average distance of 57 Å. 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× 1 2 a s〈110〉. They can be explained by a model for the correlated nucleation of misfit dislocations in highly mismatched heterostructures like ZnTe/GaAs.