Variable range hopping conductivity in hydrogenated amorphous silicon thin film transistors

Electron conduction in the accumulation layer of hydrogenated amorphous silicon (a-Si) thin film transistors shows a transition from activated band conduction to variable-range hopping, for temperatures below approximately 240°K. The observed T- 1 3 temperature dependence suggests that the hopping takes place in a two-dimensional (2-D) layer close to the a-Si/gate dielectric interface. This is consistent with the calculated conducting channel thickness of 8.5 Å to 60 Å, for the range of gate voltages used. The present results are also consistent with previously reported 2-D variable range hopping conductivity in thin amorphous semiconductors. © 1989.