Control of the Electron and Hole Drift mobilities in Plasma Deposited a-Si:H

Abstract

ABSTRACTThe ‘time-of-flight’ technique measured electron and hole drift mobilities are shown to be independent of deposition parameters in capacitively coupled, diode type RF-PECVD a-Si:H. However, the carrier mobilities can be varied by orders of magnitude by changing the bias applied to the mesh type controlling electrode in a triode type reactor. The room temperature hole drift mobility increases to 10−1cm2/Vs when an appropriate bias is applied to the mesh providing optimum energy ion stimulation of the film growth surface during deposition. Analysis of the field and temperature dependences of the drift mobilities shows that in the best specimens the conduction (valence) band tail density of states are approximately exponential with a reciprocal slope of lOMeV (25MeV).