Persistent photoconductivity in nitrogen-doped p-type Zn(S)Se/GaAs heterojunctions

Nitrogen-doped p-type ZnSe grown by molecular beam epitaxy on p-type GaAs shows persistent photocurrent up to room temperature. A typical decay consists of an initial stretched-exponential transient with a thermally activated decay constant, and a subsequent long transient. We attribute the effect to metastable centers in the ZnSe near the interface to the GaAs substrate, on the one hand, and tunneling of photo-excited holes trapped in a two-dimensional quantum well at the heterojunction through the barrier to the ZnSe, on the other hand