Electron drift mobility in a-Si:H prepared by hot-wire deposition

We have measured the electron drift mobility in a-Si:H prepared by hot wire (HW) deposition using photocarrier time-of-flight. Initial work has shown that light-soaked HW material can have much better ambipolar diffusion lengths than the plasma-deposited material following extended light soaking. In a sample with about 2% H-concentration in the intrinsic layer, we find that the electron drift mobility is quite different from that of a-Si:H alloys prepared by normal glow-discharge CVD, even allowing for the reduced bandgap of the hot wire material. This result challenges the principle that the bandgap of optimized amorphous silicon based material is sufficient to predict the electron drift mobility.