Deep UV Metal-Semiconductor-Metal Photodetectors Using Low-Temperature-Grown AlN Epilayer on Sapphires

The metal-semiconductor-metal (MSM) deep ultraviolet (DUV) photodetectors were demonstrated on epitaxial AlN films grown on c-plane sapphire by helicon sputtering system at low temperature of 300 degrees C. The dark current of the device is as low as 759 fA at 20 V bias and the photocurrent radiated with a D-2 lamp increases more than two orders of magnitude. The photocurrent increases almost linearly with the light power. The fairly good responsivity was estimated to be about 0.3 mA/W. The AlN MSM photodetector exhibits peak responsivity at 200 nm and shows a DUV/visible rejection ratio of about two orders of magnitude. The results indicate that AlN based MSM photodetectors on sapphire substrates, prepared by low temperature helicon sputtering method, are suitable for deep UV detection.