Determination of deep levels in semi-insulating cadmium telluride by thermally stimulated current measurements

Abstract

Thermally stimulated current (TSC) measurements have been performed in high resistivity (ϱ ≈ 107 ωcm) CdTe γ‐ray detectors between 35 and 300°K. The TSC curves have been analysed by different methods, including those taking into account the retrapping of the carriers. The traps characteristics have been determined; especially three levels located at Ev + 0.13 eV, Ev + 0.30 eV, and Ec − 0.55 eV have been investigated.

Characterization of undoped high resistivity CdTe grown by a THM method

“…Three peaks are clearly resolved, located at 115, 140 and 195 K. For comparison, on figure 2, we have plotted the TSC curves obtained under identical conditions for chlorine compensated crystals of different origins. It is interesting to notice that these spectra have all the same structure, similar to that reported recently [3,4]. The same peaks are present like in undoped materials, however, two additionnal peaks can be observed, located at 100 and 155 K. These results have also been compared to those obtained for indium compensated crystals of different origins.…”

“…When the temperature of the device is increased linearly as a function of time (at a rate 03B2), the trapped carriers are reemitted at a temperature which depends on the activation energy of the center. This technique was successfully applied to compensated CdTe [3,4]. The experimental results, obtained for two different undoped crystals are reported on figure 1.…”

“…All the experimental results have been summarized in table I. The energies of the peaks have been esti- TABLE 1 mated by using either different classical methods [5] or by a special procedure [3,6], which allowed us to identify the type of carrier which is trapped. The centers located at Ec -0.23 eV, 0.30 eV and E, + 0.40 eV are present in all crystals.…”

Characterization of CdTe with photoelectronic techniques

“…It could also correspond to a charged V cdIncd complex [25]. The capture crosssection reported here (see Table II) is much smaller than previously quoted [4]. The same consideration holds for the level at 0.144 eV [4].…”

“…The capture crosssection reported here (see Table II) is much smaller than previously quoted [4]. The same consideration holds for the level at 0.144 eV [4]. The level at 0.26 eV, which should also correspond to an acceptor, has been detected only by one author [5].…”