Electrical Properties of Cadmium Telluride Films and the Al/CdTe Based Schottky Barrier

Abstract

It is shown that with an increase in the thickness of cadmium telluride films from 0.4 to 1 μm, the resistivity decreases from 8·108 to 8,1·107 Ohm·cm. It is equivalent to an increase in conductivity from 1,25·10-9 to 1,23·10-8 Ohm-1· cm-1. The resistivity and conductivity change only slightly at thicknesses above 1 μm.
 One broad maximum is observed on the X-ray diffraction pattern at film thicknesses D=0.4 μm. This indicates the imperfection of the crystallites. As the thickness increases to 1 μm, a number of clear reflections with increasing intensity appear on the X-ray diffraction pattern, which is associated with the improvement of the crystal structure of the films.
 The current-voltage characteristic of the Schottky diode is obtained. It is shown that with an increase in the forward displacement, a significant increase in the forward current is observed, as well as a noticeable increase in the reverse current with a reverse displacement. The initial section of the forward characteristic at voltages up to 10 V is linear, which is inherent in Schottky barriers. However, the characteristic becomes non-linear at high voltages.
 The nonlinearity of the current-voltage characteristic of the Schottky barrier in a fairly wide range of applied voltage is related to the grain boundary effect in polycrystalline films. Namely, as the applied voltage increases to a certain value, the density of trap states in the region of the crystallite boundary decreases; holes begin to fill, which is usually observed in semiconductors containing conductive particles in a non-conductive matrix. We used this effect when studying the possibility of manufacturing nuclear radiation detectors with a metal — semiconductor — metal structure.