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, four times greater than for MoOx/n-CdTe heterostructures. The greater value of the potential barrier height is due to the formation of an electric dipole at the heterointerface owing to increased surface state concentration, associated with the presence of zinc atoms in the space charge region and at the metallurgical boundary. In МоOx/n-Cd1-хZnхTe heterojunctions, dominant current transfer mechanisms include generation–recombination and tunneling–recombination via 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: Voc = 0.3 V, Isc = 1.2 mA/cm², and FF = 0.33 at illumination 80 mW/cm², are promising for detectors of various types of radiation. Impedance measurements at various reverse biases enabled determination of the surface state density distribution and charge-exchange characteristic time, both decreasing with increasing reverse bias.