**1. Introduction**

The wide gap II–VI telluride compounds (CdTe, ZnTe, CdZnTe) are widely used as materials for different applications such as in solar and high power energetic detectors. The development of epitaxial technologies allows realizing the growth of high quality II–VI compound layers on different substrates. This gives the possibility to create multilayer structures on large in diameter widely used GaAs and Si substrate. The one of the important application of CdTe (CdZnTe) layers on GaAs substrate is as alternative substrate for sequence growth of photosensitive material mercury cadmium telluride (MCT) solid solutions [1–3]. This material is very attractive for development and production of thermal imagers that used in civilian life for medical, agricultural, chemical, metallurgical fuel industries, cosmic, etc. The MCT structures on large in diameter GaAs substrates are markedly reduce the cost of the MCT epitaxial photosensitive material and applied to creation large (up to megapixel size) focal plane arrays.

Molecular beam epitaxy (MBE) is the most appropriate epitaxial method of growing MCT layers due to its low growth temperatures (~180°C), which prevents the diffusion of impurities from the substrate and reduces the background doping [4]. But the dissociation and re-evaporation of diatomic Te molecules on singular surface at such growth temperatures is very low [5]. To increase the dissociation of diatomic Te molecules it is necessary to provide growth on vicinal surfaces. The development of multi-chamber MBE set allows carrying out the growth of MCT structures on GaAs with preliminary deposited CdTe layer in one process without uploading at air atmosphere. At the growth of CdTe on GaAs substrate t is necessary to solve the physical-chemical and technological problems. The physicalchemical problems are determined by the great differences in mismatch and nature of chemical bonding of conjugation CdTe and GaAs. In first problem the relaxation of induced stress lead to equilibrium state with introducing dislocation. In second ones the appearance of crystalline defects determined by the interaction of molecular beam Cd and Te2 with atomically clean GaAs surface. Actually the investigation of the initial stage of the CdTe growth on GaAs surface showed the formation of different mixture of orientation that seems connected with large mismatch and different surface superstructures which formed at Te interaction with GaAs [6]. The nucleation of one orientation reached by growing of ZnTe layer on GaAs surface with the sequence growth of CdTe layer.

The purpose of the chapter is to present the study of processes for high quality growth of CdTe on (013)GaAs substrate.
