Metastable Electronic Effects in Amorphous Semiconductor Superlattices

This paper reviews some of the novel electronic effects observed in amorphous semiconductor superlattices. Quantum size effects have been reported in compositionally modulated amorphous semiconductors based upon optical absorption and tunneling studies. However, the quantum well effects are in direct conflict with transport data estimates of the inelastic scattering length. In doping modulated amorphous semiconductors, a large persistent photoconductivity PPC is observed, which cannot be explained by the field separation model alone, but rather requires the presence of a defect which undergoes a large lattice relaxation upon trapping a charge (similar to the DX center). Studies of npnp amorphous silicon multilayers have enabled a microscopic determination of the process responsible for PPC.