Persistent photoconductivity in doping-modulated amorphous semiconductors

We have synthesized amorphous-semiconductor superlattices consisting of alternating layers of n-type and p-type doped, hydrogenated, amorphous silicon. These new amorphous semiconductor structures exhibit a long-lived (τ∼days) excess conductivity after a brief light exposure at room temperature. This effect may be attributed to spatial separation of the photocarriers by the pn junction fields or, alternatively, to defect centers having a barrier against retrapping of photoexcited carriers.