A simple approach to the capacitance technique for determination of interface state density of a metal-semiconductor contact

In this study we attempt to interpret the experimentally observed nonideal Al-pSi Schottky diode I-V and C-V characteristics. The expressions for the capacitance-voltage relationship at low frequency and high frequency are derived considering two non idealities, namely interface states and series resistance. After extracting the diode parameters from the I-V and C-V characteristics, theoretical plots for the high frequency and low frequency capacitance are obtained using the expressions derived. A comparison of the latter with available experimental plots reveals that the expressions for the low frequency and high frequency capacitance derived here are simpler, more accurate and closer to experimental results than those used in the past. The variation of interface state density with the applied bias voltage is obtained from the low frequency and high frequency C-V plots by using the capacitance technique. To examine the validity of the present approach, the value of density of interface states is compared with that obtained by the multifrequency admittance method. It is observed that there is good agreement between the results obtained by both methods. (C) 1998 Elsevier Science Ltd. All rights reserved.