Effect of He plasma treatment on the rectification properties of Al/CdTe Schottky contacts

We investigated the effect of He plasma treatment on the surface composition of CdTe and the electrical properties of Al/CdTe Schottky contacts. The composition of the initial CdTe surface is Te-rich due to Br-methanol etching. When Al Schottky contacts are formed on the CdTe surfaces with the Te-rich layer, the barrier height is low and the rectification property is not good. In this paper, we propose the He plasma treatment method to remove the Te-rich layer. From X-ray photoelectron spectroscopy measurement, it was found that the plasma treatment can remove the Te-rich layer. The rectification property of the Al Schottky contacts on the plasma-treated surfaces is improved, and their barrier heights are estimated to be about 0.65 eV. In gamma-ray spectrometry, a high-energy resolution of 1.6 keV full width at half maximum at 59.5 keV was obtained from the plasma-treated Al/CdTe/Pt detector. The results indicate that the plasma treatment of CdTe surfaces significantly improves the energy resolution of Schottky-type Al/CdTe/Pt radiation detectors.