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 МоOx/n-Cd1-хZnхTe semiconductor heterojunctions made by depositing MoOx films on a pre-polished surface of n-Cd1-хZnхTe 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 МоOx/n‑Cd1‑хZnхTe heterojunctions have a large potential barrier height at room temperature (φ0 = 1.15 eV), which significantly exceeds the analogous parameter for the МоOx/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 MoOx/n-CdTe heterostructures. The greater value of the potential barrier height of the МоOx/n-Cd1-хZnхTe 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 MoOx/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 МоOx/n‑Cd1-хZnхTe 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 МоOx/n-Cd1-хZnхTe heterojunctions, which have the following photoelectric parameters: open circuit voltage Voc = 0.3 V, short circuit current Isc = 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 МоOx/n-Cd1-хZnхTe 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.