Electron and hole transport in CVD Si₃N₄ films

Abstract

This letter reports on the finding that holes are more mobile than electrons in chemically vapor deposited (CVD) Si3N4. MIS structures with Si3N4 films as the insulating layers are used in the experiments. Holes are shown to be electrically injected from the silicon into the insulator when the aluminum-gate electrode is pulsed negative, and electrons when pulsed positive, with subsequent trapping in the nitride. The centroid of the trapped-hole distribution, X̄h, and that of the trapped-electron distribution, X̄e, as functions of the voltage pulse amplitude and duration are measured. The ratio of X̄h/ X̄e increases with the amplitude of the pulse and its duration, where the centroids are referenced from the injection source, and exceeds 3 when the hole distribution spans the entire nitride thickness. Data suggest that hole traps are perhaps shallower than electron traps, hence the enhanced hole conduction in the silicon nitride.