Improved solar-blind external quantum efficiency of back-illuminated Al/sub x/Ga/sub 1-x/N heterojunction pin photodiodes

摘要

Improved external quantum efficiency for Al/sub x/Ga/sub 1-x/N solar-blind pin photodiodes is reported. The zero-bias external quantum efficiency was 53% (R/sub /spl lambda// = 0.12 A/W) at 275 nm, and increased to 58% (R/sub /spl lambda// = 0.13 A/W) at a reverse bias of 5 V. In addition, the photodiodes exhibited a low dark current density of 8.2 /spl times/ 10/sup -11/ A/cm/sup 2/ at a reverse bias of 5 V, which resulted in a large differential resistance. The high zero-bias responsivity and large differential resistance combine to yield a high detectivity of D* /spl sim/ 3.0 /spl times/ 10/sup 14/ cm /spl middot/ Hz/sup 1/2/ /spl middot/ W/sup -1/. These results are attributed to an improved Al/sub 0.6/Ga/sub 0.4/N window n-region.