Effects of oxygen plasma treatment on Cd1-xZnxTe material and devices

Surface passivation in detectors is designed to improve the performance and stabilize the characteristics over time and ambient. In Cd1-xZnxTe radiation detectors, oxidation by plasma is a well-known passivation method, but its physics is not fully understood. This study focuses on the macroscopic and microscopic effects of plasma treatment. It is shown that plasma oxidation before contact deposition causes a considerable decrease in the device's dark current and that this reduction is in a strong correlation with the lowering of the surface potential. X-ray photoelectron spectroscopy (XPS) measurements revealed a significant increase in TeO2 fraction on the plasma-treated surface. The main conclusion of this study is that the plasma-related effects are not confined to the surface layer. Furthermore, the deep penetration of plasma treatment byproduct takes place over long time periods, which may lead to variations in device characteristics. The effects were corroborated by several characterization techniques. DC current-voltage measurements combined with layer-by-layer stripping indicate plasma signature deep into the bulk. Transient current technique (TCT) results demonstrate that the plasma treatment affects the electric field distribution millimeters into the bulk. Photo-induced current transient spectroscopy (PICTS) and thermoelectric emission spectroscopy (TEES) measurements reveal plasma-related traps in-depth of the CdZnTe crystals.

Automated summary

The study demonstrates that plasma treatment has significant effects on the performance and characteristics of Cd1-xZnxTe radiation detectors, especially in terms of dark current reduction. Plasma oxidation increases the oxide fraction on the surface, lowering the device's dark current, and may cause variations in device characteristics over long periods. The effects of plasma treatment penetrate deep into the bulk of the detector and can be observed through various characterization techniques.