Deep levels in high resistive CdTe and CdZnTe explored by photo-Hall effect and photoluminescence spectroscopy

Abstract

High resistive CdTe and CdZnTe single crystals were measured by photo-Hall effect spectroscopy (PHES) and photoluminescence spectroscopy (PL) with the aim of discovering the position of deep levels (DLs) in the band gap. Illumination in the range of 0.65–1.77 eV, room temperature, and DC electrical measurements were used in the case of PHES. Low temperature (4 K) photoluminescence spectra were recorded in the spectral range above 0.47 eV. Eight samples, both n-type and p-type, were studied and typical shapes of spectra were collected, compared and interpreted for both spectroscopy methods. It was shown that a simple single-level model of PHES often fails in the interpretation of DLs distant from the midgap. Eight DLs with the energy Ec − 0.65 eV, Ec − 0.8 eV, Ec − 0.9 eV, Ec − (1.10–1.15) eV, Ev + 0.70 eV, Ev + 0.85 eV, Ev + 1.0 eV, and Ec − 1.25 eV were interpreted. A memory effect characterized by a relaxation time of about 60 s was observed at the 0.8 eV level and allowed us to determine the 1.7 × 10−17 cm2 capture cross-section of electrons on this level. It is argued that PHES is a convenient complementary method to identify and characterize DLs, including DLs inaccessible by thermal emission techniques. DLs observed by PHES were consistently verified by PL.