Formation and characterization of Au-Al2O3-native oxide-HgCdTe structures

The work is devoted to an investigation of Al₂O₃ deposition on chemically treated and oxidized surfaces of HgCdTe. Also, platinum deposition on thin (<; 2 nm) Al₂O₃ layer was observed. Chemical composition of the surfaces was studied by X-ray photoelectron spectroscopy (XPS) in situ without exposure at an ambient atmosphere. High frequency CV characteristics of Au - 50 nm Al₂O₃-1 nm native oxide - HgCdTe structures and IV characteristics of Au- 2 nm Al₂O₃ - 1 nm native oxide - HgCdTe structures were analyzed. It was established that presence of native oxide on a HgCdTe surface leads to decrease of mercury depletion, but oxide thickness decreases during Al₂O₃ e-beam physical vapor deposition (EBPVD). The MIS structures with 50 nm aluminum oxide on HgCdTe and gold contacts have negative fxed charge ~ 2·10¹² cm^-2. In the case of native oxide interlayer existence density of fxed charge is lower. Large hysteresis of CV characteristics is observed. The structures with tunnel insulator are rectifying at temperature of 90K. The ideality factor and the barrier height determined from forward-bias current-voltage characteristics were 4.3 and 0.17 eV respectively. Reverse-bias IV doesn´t tend to saturation because of existence of a barrier lowering mechanisms complex.