Role of Surface on the Persistent Photoconductivity in Porous Silicon and Boron Doped a-Si:H

The effect of ambient conditions on light soaking (LS) in porous silicon (PS) sample is studied. In vacuum LS on porous silicon increases dark current (DC) while in presence of water vapor it decreases DC. Interestingly, LS gives a higher DC in vacuum as well as in presence of water vapor for boron doped hydrogenated amorphous silicon a-Si:H(B) samples. A thin layer of polystyrene polymer almost eliminates the light induced degradation of porous silicon (PS) layers but can do so only to a smaller extent in a-Si:H(B). This shows that the effect of LS in PS is different than the effect of LS in a-Si:H(B) and that the surface plays a more important role in PS than in a-Si:H.