Comparative study of In/CdTe/Au Schottky- and p-n junction-diode detectors formed by backside laser irradiation doping

Two types of In/CdTe/Au diode structures were fabricated using detector-grade p-CdTe single crystals: (i) by vacuum evaporation of In and Au contacts on the chemically treated (111) surfaces; (ii) by backside laser doping when the In/CdTe structures were irradiated from the crystal side with a wavelength for which the semiconductor was transparent. Thus, diodes with a Schottky contact (In/CdTe) and a p-n junction were obtained, respectively. To prove the doping of the thin region near the In/CdTe interface by In (donor) and study thermal tolerance of both types of In/CdTe/Au diode detectors, room temperature I-V characteristics and Co-57 isotope emission spectra were measured before and after annealing of the diodes at temperatures below and above the In melting point. Thermal annealing at lower temperatures led to a slight increase and decrease in reverse dark current of the unirradiated and laser-irradiated samples, respectively. Heating up to 200 degrees C resulted in a significant increase in reverse current and complete spectra degradation in the samples fabricated without laser processing. After such annealing, the electrical characteristics of the p-n junction diodes, formed by the backside laser doping technique, became optimized and Co-57 spectra were almost unchanged. It was supposed that a Schottky barrier at the In/CdTe interface was degraded, while a p-n junction, created in a deeper region of the CdTe crystal, remained functional even after melting and solidifying the In contact.