Properties of CdTe<i>p</i>-<i>n</i>Diodes Prepared by Al Vapor-Diffusion

Abstract

Aluminium vapor-diffused p–n diodes in CdTe have been shown to have abrupt and smooth junctions, and emit efficient electroluminescence at 77 K. Moreover, the p-type region of the diodes has relatively low resistivity (about 30 ohm-cm) and good ohmic contact prepared by an evaporation of Au (or Pt). The low average concentration of majority carriers at a junction is up to 1.7×1017 cm-3. It is shown that the forward current of the diodes at low current density is due to band-impurity tunneling at 77 K, whereas it arises from thermal processes involving recombination in the space-charge region at 300 K. The reverse current appears to be dominated by tunneling under all of the measured bias-voltage ranges at 77 K and under a high bias range at 300 K. A deep trapping center detected by TSCAP has an energy depth of about 0.68 eV above the valence band edge and concentrations between 3.3×1015 and 2.6×1016 cm-3.