Low noise p-π-n GaN ultraviolet photodetectors

We report on the fabrication and characterization of $\mathrm{p-\pi -n}$ GaN ultraviolet detectors. The peak responsivity at $\text{∼363 \hspace{0.17em}}\mathrm{nm}$ is measured to be 0.1 A/W in the photovoltaic mode, and 0.14 A/W with a bias of −15 V. Speed measurements have shown the photoresponse to be RC-limited with the response time decreasing from 17.4 ns at zero bias to 10.3 ns at −6 V bias. For a $\text{200×200 μ\hspace{0.17em}}{\mathrm{m}}^2$ device, we measure the dark current to be 2.7 pA at −3 V bias, and a noise density of less than ${10}^{\text{−25}}\hspace{0.5em}{\mathrm{A}}^2/\mathrm{Hz}$ , the noise floor of the measurement. Extrapolating the noise data taken at higher reverse biases, we estimate the noise equivalent power to be ${\text{6.6×10}}^{\text{−15}}\hspace{0.5em}{\mathrm{W/Hz}}^{\text{1/2}}$ .