Oxygen–induced barrier height changes in aluminium – amorphous selenium Schottky diodes

Abstract

The effects of thin and thick oxides on Aluminium – Selenium (Al-Se) diodes have been investigated. Selenium films of thickness 1000Å were deposited by thermal evaporation in a vacuum of about 10-5 torr. Thereafter, oxide films were intentionally grown on the amorphous selenium (a-Se) films by exposing the samples to oxygen before the aluminium contacts were deposited. Current – voltage (I-V) measurements were carried out on the samples. The results show that the application of voltage causes charge exchange between the surface states and the semiconductor leading to a change in the height of the potential barrier for electrons passing from aluminium into the a-Se films. The empirically determined values of barrier height of Al/a-Se diodes with thin and thick oxide layers are 1.15 and 1.00 eV respectively. The thin oxide layer has a thickness of 15Å while the thickness of the thick oxide layer is 50Å. Also, the analysis of the I-V characteristics of Al/a-Se contacts reveals that they exhibit rectifying properties and therefore can be used as rectifiers. Keywords: Semiconductor, thermal evaporation, diode, rectifier, oxide film Botswana Journal of Technology Vol.13(1) 2004: 51-54