The influence of substrate temperature on electrical properties of Cu/CdS/SnO2 Schottky diode

Abstract

Polycrystalline CdS samples on the SnO2 coated glass substrate were obtained by vacuum evaporation method at low substrate temperatures (T S=200 and 300 K) instead of the commonly used vacuum evaporation at high substrate temperatures (TS>300 K). X-ray diffraction studies showed that the textures of the films are hexagonal with a strong (0 0 2) preferred direction. Circular Cu contacts were deposited on the upper surface of the CdS thin films at 200 K by vacuum evaporation. The effects of low substrate temperature on the currentvoltage (IV) characteristics of the Cu/CdS/SnO 2 structure were investigated in the temperature range 100300 K. The Cu/CdS (at 300 K)/SnO2 structure shows exponential currentvoltage variations. However, IV characteristics of the Cu/CdS (at 200 K)/SnO2 structure deviate from exponential behavior due to high series resistance. The diodes show non-ideal IV behavior with an ideality factor greater than unity. The results indicate that the current transport mechanism in the Cu/CdS (at 300 K)/SnO2 structure in the whole temperature range is performed by tunneling with E00=143 meV. However, the current transport mechanism in the Cu/CdS (at 200 K)/SnO2 structure is tunneling in the range 200300 K with E00=82 meV. © 2011 Elsevier B.V.