Electrical properties of SiO2 and Si3N4 dielectric layers on InP

Abstract

Plasma-enhanced chemical vapor deposition techniques using SiH4 and N2O have been employed to deposit SiO2 insulating layers on n-type InP substrates. Si3N4 layers have been deposited employing the reaction between SiH4 and NH3. Metal-insulator-semiconductor capacitors have been fabricated from these structures and their interfacial properties have been measured using capacitance-voltage techniques. The amount of surface potential modulation achieved using SiO2 layers is process dependent and varied from 0.4 to 1.2 V. The modulation observed using Si3N4 layers was consistently about 0.6 V. The amount of trapped interfacial charge in the SiO2 layers is shown to be given by a fixed charge plus a charge directly proportional to the electric field in the oxide. A compilation of data for SiO2 layers on other semiconductors, including silicon, illustrates that this is apparently a universally-observed phenomenon. It is shown that this charging behavior gives the familiar u-shaped density of states curve. As an alternative to the present method of characterizing interfacial charging behavior, an interfacial quality factor ΔQss/ΔQsc is proposed that is independent of the semiconductor band gap or impurity level.