Quantum Yield of GaN and (Ga, Al)N Band-Gap Graded Ultraviolet p–n Detectors

Abstract

Calculation of the quantum yield has been carried out for an AlxGa1—xN(n)–GaN(p) photodiode as an ultraviolet detector with energy band-gap graded (EBGG) AlxGa1—xN(n) layer. The analytical solution of the one-dimensional continuity equation was used in the calculation. The spatial dependence of the material properties, such as the absorption coefficient and the energy band-gap of the n-type layer of the photodiode is included in the solution. The band-gap grading due to a reduced absorption coefficient at the surface region (where recombination occurs) and the built in electric field results in an increase of the generated minority carrier collection efficiency. Within the range of small values of EBGG there is a substantial rise in the detector quantum yield with increasing grading. In the case of surface recombinationless AlxGa1—xN(n) front side layer, the further increase of the grading does not result a significant rise of quantum yield, especially in the spectral region near to the cutoff. Much more pronounced increase in quantum yield with a grow of the grading has neem found when the surface recombination was represent.