TEMPERATURE-DEPENDENCE OF I-V AND C-V CHARACTERISTICS OF AL CDTE SCHOTTKY DIODES/

A comparative study was made of rf-sputtered Al on chemically-etched ( CE) and sputter-etched (SE) p-CdTe single crystal surfaces. By means o f measuring current-voltage, capacitance-voltage and deep level transi ent spectroscopy (DLTS) characteristics of rf-sputtered A1/p-CdTe Scho ttky junctions formed on both surfaces, it has been found that surface preparation techniques can alter the Schottky junction properties. Th e I-V measurements are seen to closely follow the diode equation of Sc hottky barrier diodes dominated by thermionic emission. This model is confirmed by activation energy measurements. Diode factors of about 1. 05 and 1.15, and barrier heights of about 0.63 and 0.75 eV were obtain ed for C and SE junctions respectively. The dependence of C-2 vs V for both junctions was found to be almost linear and the slope of the plo ts yielded a doping density of about 2.6 x 10(15) and 1.2 x 10(15) cm( -3) for CE and SE junctions respectively. Both junctions show a freque ncy dispersion at low frequencies which is due to traps in the surface region. Also deep traps can have effects on the capacitance depending on trap depth, concentrations and locations. This is exploited in the DLTS measurements in the temperature range 100-300K, which indicated the presence of deep trap levels around 0.55 eV above the valence band for both CE and SE Schottky diodes. Such deep levels are known to inf luence the electrical properties of II-VI compound semiconductors.