Electrical and Photoelectric Properties of Heterojunctions MoOx/n-Cd1-xZnxTe

Abstract

The paper presents the results of studies of the optical and electrical properties of МоO_x/n-Cd_1-хZn_хTe semiconductor heterojunctions made by depositing MoO_x films on a pre-polished surface of n-Cd_1-хZn_хTe plates (5 × 5 × 0.7 mm³) in a universal vacuum installation Leybold - Heraeus L560 using reactive magnetron sputtering of a pure Mo target. Such studies are of great importance for the further development of highly efficient devices based on heterojunctions for electronics and optoelectronics. The fabricated МоO_x/n‑Cd_1‑хZn_хTe heterojunctions have a large potential barrier height at room temperature (φ₀ = 1.15  eV), which significantly exceeds the analogous parameter for the МоO_x/n-CdTe heterojunction (φ₀ = 0.85 eV). The temperature coefficient of the change in the height of the potential barrier was experimentally determined to be d(φ₀)/dT = -8.7·10^-3 eV K, this parameter is four times greater than the temperature coefficient of change in the height of the potential barrier for MoO_x/n-CdTe heterostructures. The greater value of the potential barrier height of the МоO_x/n-Cd_1-хZn_хTe heterojunction is due to the formation of an electric dipole at the heterointerface due to an increase in the concentration of surface states in comparison with MoO_x/n-CdTe heterostructures, and this is obviously associated with the presence of zinc atoms in the space charge region and at the metallurgical boundary section of the heteroboundary. In МоO_x/n‑Cd_1-хZn_хTe heterojunctions, the dominant mechanisms of current transfer are generation-recombination and tunneling-recombination with the participation of surface states, tunneling with forward bias, and tunneling with reverse bias. It was found that МоO_x/n-Cd_1-хZn_хTe heterojunctions, which have the following photoelectric parameters: open circuit voltage V_oc = 0.3 V, short circuit current I_sc = 1.2 mA/cm², and fill factor FF = 0.33 at an illumination intensity of 80 mW/cm² are promising for the manufacture of detectors of various types of radiation. The measured and investigated impedance of the МоO_x/n-Cd_1-хZn_хTe heterojunction at various reverse biases, which made it possible to determine the distribution of the density of surface states and the characteristic time of their charge-exchange, which decrease with increasing reverse bias.