We have studied the effect of sulfur treatment on the performance of a CdTe radiation detector with an Al Schottky electrode. After sulfur treatment, the leakage current was 1:51 Â 10 À9 A at a bias voltage of 250 V, whereas that of a sample without sulfur treatment was 7:90 Â 10 À9 A. Moreover, samples with sulfur treatment were capable of measuring the -radiation from 241 Am for 150 min, while samples without sulfur treatment were incapable of measuring the -radiation after 30 min. The improvement in the polarization of the CdTe radiation detector was achieved by the sulfur treatment of the CdTe surface.

We investigated the effect of plasma treatments using He and H 2 gases on the electrical properties of Schottky CdTe diodes. The composition of the initial CdTe surface was Te-rich owing to Br-methanol etching. However, after the plasma treatments, the Te-rich layer was removed from the CdTe surface and the surface composition became stoichiometric. The plasma treatment improved the rectification properties of the Al Schottky CdTe diode. Furthermore, by adopting a guard-ring electrode, the reverse current of the CdTe diode decreased by more than one order compared with that of the CdTe diode without a guard-ring electrode. We evaluated the barrier height and ideality factor from current-voltage characteristics. The barrier heights of the CdTe diodes after He and H 2 plasma treatments were 0.75 and 0.73 eV, respectively.

High energy-resolution CdTe radiation detectors with Schottky contact show instability with operating time under bias voltage, which is termed as polarization phenomenon. Time stability is one of the important factors for its practical applications. It is considered that this phenomenon is responsible for the deep acceptor level in CdTe bulk. However, the energy position and concentration of the deep acceptor level have been not estimated accurately. We have studied the polarization phenomenon and the parameters of deep acceptor in a Schottky-type CdTe radiation detector. In this paper, we propose a new method which can quantitatively evaluate the parameters of the deep acceptor such as concentration and energy level by measuring the temperature dependence of the current-voltage characteristics of the CdTe radiation detector.