Effects of substrate preheating for the growth of ZnxCd1-xTe/(100)GaAs by MOCVD

A process for the growth of ZnCdTe/(1 0 0)GaAs heteroepitaxial films using metalorganic chemical vapor deposition (MOCVD) has been developed. It is found that substrate baking pretreatment deeply affects the characteristics of ZnxCd1-xTe (x < 0.09) on (1 0 0)GaAs substrate (such as ZnCdTe film orientations, the Zn composition in the ZnCdTe compound alloys and the quality of ZnCdTe epilayer). We compared measurements on the same set of samples by photoreflectance (PR) and photoluminescence (PL). It was found that baking temperature (or baking time) may affect the relative contribution of each transition, resulting in a shift of the transition energy. We speculate that (1 0 0)GaAs substrates may undergo decomposition at a high baking temperature, leading to the GaAs surface change from As-stabilized surface to Ga-stabilized surface, resulting in better film PL quality and different film orientation. At higher baking temperature (or baking time), the ZnCdTe epilayer tends towards a (1 1 1) orientation and the film quality is obviously improved. Up to a temperature of around 640 degrees C, the quality begins to decline sharply due to the destruction surface.