Study of charge trapping instabilities in a silicon-nitride/indium-phosphide metal-insulator-semiconductor structure by the constant-capacitance method

Abstract

The applicability of the constant-capacitance method to the characterization of the charge trapping mechanisms in the insulator of a metal-insulator semiconductor (MIS) is demonstrated. It is simple, time saving, and particularly useful in a III-V compound semiconductor MIS where the density of fast interface states may be high. Under constant capacitance, the measured diode current is directly related to the average distance that the injected charges travel before being trapped within the insulator. This method was applied to Al/silicon-nitride/InP MIS capacitors where silicon nitride films were formed by plasma-enhanced chemical-vapor deposition (PECVD). From the measurements, it was found that charge trapping by direct tunneling is dominant near the silicon-nitride/InP interface under a low insulator field, and the injection of electrons to the bulk of the silicon nitride assisted by the electric field occurs at a higher insulator field. It is also confirmed that the trap density near the silicon-nitride/InP interface is higher than that of the silicon-nitride bulk due to the initial transient phenomena of the PECVD process.