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 of measuring current-voltage, capacitance-voltage and deep level transient spectroscopy (DLTS) characteristics of rf-sputtered A1/p-CdTe Schottky junctions formed on both surfaces, it has been found that surface preparation techniques can alter the Schottky junction properties. The I-V measurements are seen to closely follow the diode equation of Schottky 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 obtained 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 plots 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 frequency 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 influence the electrical properties of II-VI compound semiconductors.