Persistent photoconductivity from thin layer amorphous silicon doping modulated superlattices

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Abstract
Further evidence about the phenomenon of persistent photoconductivity (PPC) in doping modulated amorphous hydrogenated silicon multilayers, has been obtained by studying nipi structures with fixed p‐ (3.3 nm) and n‐ (7.7 nm) layer thicknesses but varying i‐layer thicknesses. The PPC showed a fairly sharp maximum at i‐layer thicknesses of 14 nm, being over 103 times the dark conductivity 10 min after a 20‐s light flash at 50 mW cm−2. The decay rates indicate that at least two kinds of trapping centers are involved. From the various phenomena it is proposed that the effect is due to B‐P complexes which form deep traps but become shallow after H accretion. Junctions are not directly responsible but different H concentrations in differently doped layers play a key role.