Electrical Conduction Mechanisms in n-CdS/p-CuFeO<sub>2</sub> Heterojunction Diode

Abstract

In this work, n-CdS/p-CuFeO2 heterojunction diode was fabricated by thermal evaporating CdS thin films on 1 mm thick-CuFeO2 ceramic substrate with substrate temperature kept at 373 K during evaporation process. The forward current-voltage characteristics of n-CdS/p-CuFeO2 heterojunction in a temperature range of 100-300 K were investigated to determine the electrical parameters and conduction mechanism. It was found that, at forward bias below 0.5 V, the conduction mechanism of the diode is dominated by thermionic emission (TE) mechanism. At bias voltage above 0.5 V, the current transport is due to space charge limited current (SCLC) controlled by an exponential trap distribution in the band gap of CdS. The temperature dependence of the saturation current and ideality factor are well described by tunneling enhanced recombination at junction interface with activation and characteristic tunneling energy values as about 1.79 eV and E00 = 86 meV, respectively. The value of interface state density (Nss) evaluated from capacitance spectroscopy increases from 2.09x1011 eV-1cm-2 (at 300 K) to 2.70x1011 eV-1cm-2 (at 363 K). Free carrier concentration of 5.80x1013 cm-3 at room temperature was estimated from capacitance-voltage measurements at 50 kHz.