On the energy distribution of interface states and their relaxation time and capture cross section profiles in Al/SiO2/p-Si (MIS) Schottky diodes

The energy distribution profile of the interface states (Nss) and their relaxation time (τ) and capture cross section (σp) of metal–insulator–semiconductor (Al/SiO2/p-Si) Schottky diodes have been investigated by using the high–low frequency capacitance and conductance methods. The capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics of these devices were investigated by considering series resistance (Rs) effects in a wide frequency range (5 kHz–1 MHz.). It is shown that the capacitance of the Al/SiO2/p-Si Schottky diode decreases with increasing frequency. The increase in capacitance especially at low frequencies results form the presence of interface states at Si/SiO2 interface. The energy distributions of the interface states and their relaxation time have been determined in the energy range of (0.362-Ev)–(0.512-Ev) eV by taking into account the surface potential as a function of applied bias obtained from the measurable C–V curve (500 Hz) at the lowest frequency. The values of the interface state density (Nss) ranges from 2.34 × 1012 to 2.91 ×  1012 eV−1/cm2, and the relaxation time (τ) ranges from 1.05 × 10−6 to 1.58 × 10−4 s, showing an exponential rise with bias from the top of the valance band towards the mid-gap.