Electrical properties and the role of inhomogeneities at the polyvinyl alcohol-inp schottky barrier interface

摘要

In this work, we have investigated the electrical properties of Au-InP contacts with a thin layer of polyvinyl alcohol (PVA) as an interlayer. The current-voltage (I-V) and capacitance-voltage (C-V) measurements are carried out in the temperature range of 175-425 K. The Au/PVA-InP Schottky structure show nonideal behaviors and indicates the presence of a nonuniform distribution of interface states. The temperature dependent interface states densities (N SS), ideality factor n(V,T) and barrier height φb(V,T) are obtained. An abnormal decrease in zero-bias barrier height (BH) and increase in the ideality factor (n) with decreasing temperature have been explained on the basis of the thermionic emission theory with Gaussian distribution (GD) of the BHs due to the BH inhomogeneities. The experimental I-V characteristics of Au/PVA-InP Schottky diode has revealed the existence of a double GD with mean BH values of (φ?bo) of 1.246 and 0.899 eV and standard deviation (σo) of 0.176 and 0.137 V, respectively. Consequently, the modified conventional activation energy lna?(Io/T2)-(q2σo2/2kB2T2) versus 103/T plot gives φ?bo and Richardson constants (AR*) and the values are 1.17 and 0.71 eV and 9.9 and 6.9 A/cm~2 K~2, respectively, without using the temperature coefficient of the BH. The effective Richardson constant value of 9.9 A/cm~2 K~2 is very close to the theoretical value of 9.4 A/cm~2 K~2 for n-InP. The discrepancy between Schottky barrier heights estimated from I-V and C-V measurements is also discussed.