Dynamics of native oxide growth on CdTe and CdZnTe X-ray and gamma-ray detectors

Abstract

We studied the growth of the surface oxide layer on four different CdTe and CdZnTe X-ray and gamma-ray detector-grade samples using spectroscopic ellipsometry. We observed gradual oxidization of CdTe and CdZnTe after chemical etching in bromine solutions. From X-ray photoelectron spectroscopy measurements, we found that the oxide consists only of oxygen bound to tellurium. We applied a refined theoretical model of the surface layer to evaluate the spectroscopic ellipsometry measurements. In this way we studied the dynamics and growth rate of the oxide layer within a month after chemical etching of the samples. We observed two phases in the evolution of the oxide layer on all studied samples. A rapid growth was visible within five days after the chemical treatment followed by semi-saturation and a decrease in the growth rate after the first week. After one month all the samples showed an oxide layer about 3 nm thick. The oxide thickness was correlated with leakage current degradation with time after surface preparation.

Keywords:

• CdTe
• oxidation
• ellipsometry
• XPS
• leakage current

Classification:

• 40 Optical
• magnetic and electronic device materials
• 212 Surface and interfaces
• 201 Electronics / Semiconductor / TCOs

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgements

The authors would like to thank Jan Ulrych for the mechanical preparation of the samples, Karel Mašek for the XPS measurements and Martin Zahradník for the assistance during ellipsometric experiments.