Theoretical study of a potential ultraviolet avalanching detector based on impact ionization out of confined quantum states

A detailed analysis is given of a possible new ultraviolet photodetector based on impact ionization out of confined quantum states using a GaN-Al_xGa_1-xN multiple quantum well array. The GaN-AlGaN materials system is continuously gradable in composition and has a large conduction-band-edge discontinuity, which makes it an attractive candidate for asymmetric confined quantum state photomultipliers. The impact-excitation rate is determined for various device geometries and doping concentrations. As the carrier concentration increases in a quantum confined structure. the excitation probability increases. The ionization rate increase is due in part to the increase in the number of carriers within the high-energy subbands of the well with the resulting reduction of the carrier ionization threshold energy