Optically Induced Potential Fluctuations in a‐Si:H Films

The influence is studied of prolonged optical exposure on the properties of the current path in glow discharge deposited a‐Si:H films. Information on these properties is obtained from concomitant investigations of the conductivity σ and thermoelectric power S as a function of temperature. It is found that the activation energies of both quantities, Eσ and ES, increase appreciably upon light exposure. At the same time the difference Eσ — ES = EQ rises from ≈ 0.09 to 0.21 eV. The quantity EQ, which is an apparent mobility activation energy, is associated with spatial fluctuations of the mobility edge. The increase of EQ is attributed to the enhancement of potential fluctuations which is caused by inhomogeneously distributed charged centers generated during optical exposure.