Passivation Effect and Stability of Diamond-Like Carbon Film on CdZnTe Devices

Abstract

Leakage currents of a CdZnTe (CZT) detector are desired to be as low as possible for a better signal-to-noise ratio in the acquisition of x-ray/gamma-ray spectra. Surface passivation plays a major role in reduction of the surface leakage current and thereby improves the detector performance. In this paper, diamond-like carbon (DLC) film has been introduced as the passivation layer for a CZT detector. Passivation effect and stability of the DLC film on CZT devices have been investigated by the Raman spectrum, x-ray photoelectron spectroscopy (XPS), atomicforce microscopy (AFM) and current–voltage characteristic. High-quality DLC films were effectively fabricated on CZT devices measured by the Raman spectrum. The XPS in-depth profiling of CZT passivated with DLC film demonstrated that no interface reaction occurred, and DLC effectively prevented the oxidation reaction to produce the state Te4+ in Te3d spectra. Moreover, the surface leakage current evidently dropped after the DLC film passivation. In addition, properties of the DLC films with different thickness were investigated. It was shown that the effect of this passivation over stability with time is not perfect and an optimum thickness of the DLC film is proposed for reaching the best stability for CZT devices.