The effects of a high-temperature anneal on the electrical and optical properties of bulk CdTe:In

Abstract

The electrical and optical properties of bulk CdTe:In have been studied by means of van der Pauw-Hall-effect measurements and low-temperature photoluminescence (PL). As-grown, the bulk CdTe:In samples exhibited high resistivity (ρ>108 Ω cm). Following a high-temperature anneal at 900°C in a Cd overpressure, the CdTe samples became n-type (n∼1016 -1017 cm-3 at 300 K). The carrier concentration was found to depend on the anneal time. The PL spectra from as-grown samples are dominated by edge emission at 1.583-1.584 eV, the nature of which is determined from the optical measurements. As a result of the anneal, PL emission above 1.606 eV (the band gap of CdTe at 4.5 K) is observed. Excitation PL measurements, along with studies of the temperature and power dependencies of the PL emissions from the annealed samples, suggest an increase in band gap to 1.632 eV has occurred, which we believe is due to the incorporation of interstitial Cd into the lattice. Our study provides a correlation between the electrical and optical properties of bulk CdTe:In which, upon annealing, may be used as a conducting II-VI substrate in epitaxial film growth.