Planar GaN-based UV photodetectors formed by Si implantation

Planar GaN-based p-n^--n⁺ photodetectors were fabricated by Si implantation into p-GaN to form the p-n junction. Two-step triple Si implantation was performed to form a selective n⁺ and n^-area in p-GaN epitaxial layer with uniform doping profile. Therefore, a planar GaN p-n^--n⁺ UV photodetector can be achieved. When the reverse bias was below 4V, the photodetectors showed a near constant dark current around 20pA. The dark current is somewhat high compared with conventional epitaxial p-i-n photodiodes. Spectral response measurements revealed peak of responsivity up to 12.4mA/W at 365nm for the planar p-n ^--n⁺ UV photodetector. It was also found that the visible (450nm)-to-UV (360nm) rejection ratio was around 650. Furthermore, temporal response measurements for the planar GaN-based p-n^--n⁺ UV photodetector were measured to be as low as 5.7 ns for 90%-to-10% fall time.