Temperature dependence of barrier heights of Au/n-type GaAs Schottky diodes

Abstract

The forward bias current–voltage (I–V) and reverse bias capacitance–voltage (C–V) characteristics of the Au/n-GaAs Schottky diodes (SDs) are investigated over a wide temperature range of 80–400K. According to thermionic emission theory (TE) mechanism, the zero bias barrier height ΦI−V calculated from forward bias I–V characteristics was found to increase with increasing temperature. Such behavior is an obvious disagreement with negative temperature coefficient of the Schottky barrier height. However, the barrier height determined from the C2−V characteristics at high frequency decreased linearly with increasing temperature. This discrepancy between ΦI−V and Φb(C−V) can be explained by the existence of excess capacitance at MS contacts due to interfacial insulator layer or interface states. The existence of barrier height inhomogeneity offers other explanation. Therefore barrier height ΦI−V has been corrected by taking into account quality factors (n) and the electron tunneling factor (αχ1/2δ) in the expression of reverse saturation current (I0) of the diodes. Thus, corrected effective barrier height Φbef(I−V) is in good agreement with the reported negative temperature coefficient of the barrier height of Au/n-GaAs Schottky diodes.