Effects of polarisation on solar-blind AlGaN UV photodiodes

The effects of spontaneous and strain induced polarisation, and incomplete dopant ionisation on the spectral responsivity of a Ga-faced p-GaN/i-Al/sub 0.33/Ga/sub 0.67/N/n-GaN photodiode structure are determined using a commercial finite element modelling package. It is shown that polarisation induced interface charges increase the barrier to carriers generated in the GaN regions of the diode, improving the solar-blindness of the diode by more than three orders of magnitude. In contrast, incomplete dopant ionisation has only a minor effect.