Improvement of Surface Defects in CdZnTe Crystals by Rapid Thermal Annealing

Abstract

We have investigated the influence of rapid thermal annealing (RTA) on the surface defects of CdZnTe (CZT) crystals by using low-temperature photoluminescence (PL) measurements. In the low-temperature PL spectrum for the as-grown CZT crystals, the donor–acceptor pair (DAP) recombination peak is dominant. Overlapping of the free-exciton (FE) and the neutral donor bound exciton (D0,X) luminescence peaks leads to broadening of the (D0,X) peak. In the low-temperature PL spectra for CZT crystals annealed at 523 K and 623 K for 5 min, the A-center peak is dominant. The deterioration of the intensity and FWHM of the (D0,X) peak indicates worsening of the crystal quality under the two RTA conditions. In the low-temperature PL spectra for CZT crystals annealed at 723 K, 773 K and 873 K for 5 min, an FE peak gradually becomes evident as the annealing temperature increases. The full-width half-maximum (FWHM) of the (D0,X) peak decreases from 7.95 meV before annealing to 2.85 meV after annealing at 873 K. The neutral acceptor bound exciton (A0,X) peak intensity increases with the annealing temperature increasing. The peak intensity ratio I(D0,X)/I(DAP) increases from ∼ 0.24 before annealing to ∼ 1.62 after annealing at 873 K. The A-center peak intensity decreases with the increase in annealing temperature. These phenomena demonstrate better surface structure and higher crystal quality under the three RTA conditions, especially for the annealing at 873 K. RTA treatment can be an effective way to improve the surface properties of CZT crystals by modifying the technical parameters.