Comparison of electrical and luminescence data for the A center in CdTe

Abstract

We have investigated the electrical and optical properties of the deep levels responsible for the 1.4-1.5 eV luminescence band usually observed in II-VI compounds. We compared the energy levels found by cathodoluminescence and junction spectroscopy methods for semi-insulating (CdTe:Cl and Cd_(0.8)Zn_(0.2)Te) and semiconducting samples (undoped CdTe). The techniques utilized were deep level transient spectroscopy (DLTS) on semiconducting samples and photoinduced current transient spectroscopy and photo-DLTS on high resistivity materials. These last two techniques are complementary and allow the determination of the trap character (donor/acceptor). Three acceptor levels are seen in the electrical transient data at E(upsilon)+0.12, 0.14, and 0.16 eV with hole capture cross sections of 2x10^(-16), 1x10(-16), and 4X10^(-17) cm(2), respectively. The lowest level is seen only in Cl doped material corroborating the literature optical and electron spin resonance identification of a level at E_(upsilon)+0.12 eV as being a V_Cd+Cl_Te, donor-acceptor pair center. All three levels may be present in the 1.4 eV luminescence band.