Graphite/CdMnTe Schottky diodes and their electrical characteristics

The first Schottky diodes based on n-CdMnTe crystals with pronounced rectifying properties are investigated. It is shown that the I-V characteristics of the diodes fabricated by printing colloidal graphite can be described by the Sah-Noyce-Shockley theory of generation-recombination in the space charge region. Exponential increase of forward current with voltage is limited by a relatively low barrier height at the graphite/CdMnTe contact (similar to 0.4 eV) and a significant series resistance of the crystal bulk (similar to 10(6) Omega at room temperature). Tunneling due to high concentration of uncompensated impurities in investigated Cd0.9Mn0.1Te crystals (7 x 10(17) cm(-3)) does not allow increasing the reverse bias voltage to the values needed for the operation of x- and gamma-ray detectors. High concentration of uncompensated donors is interpreted by the fact that a certain part of the Mn atoms does not substitute for Cd but plays a role of over-stoichiometric impurities. In the case of the presence of a thin intermediate insulator layer in the graphite/CdMnTe contact, a rapid increase in the current for both polarities of high voltage due to the Frenkel-Poole emission is observed. The obtained results shed light on the problems of technology of growing and post-processing CdMnTe crystals regarded as a prospective material for x- and gamma-ray detectors.