Time of flight mobility measurements in a-Si:H grown under controlled-energy ion-bombardment

Abstract

The time-of-flight photoconductivity technique has been employed to evaluate the electron and hole drift mobility in a-Si:H samples prepared with varying energy-of-ion-bombardment during growth. The values of the room temperature measured hole drift mobility increases from conventional values of ≈ 0.004 cm 2/V s up to ≈ 1 cm 2/V s. The corresponding electron drift mobility increases from ≈ 1 cm 2/V s to ≈ 60 cm 2/V s. This increase is accompanied by a decrease of the mobility activation energy and an increase in its field dependence. Low-frequency capacitance—voltage measurements reveal that there is no significant change of the mid-gap defect density.