High responsivity AlGaN-based UV sensors for operation in harsh conditions

We report on high performance metal- semiconductor-metal UV photodetectors based on (Al,Ga)N grown by metalorganic chemical vapor deposition on sapphire. Thanks to a specifically studied A1N nucleation layer, high quality (ALGa)N layers have been obtained, with Al mole fraction ranging from 0 to 0.5. Due to the high epilayer quality, a photocurrent to dark current ratio as high as 103 was found with Cr/Au Schottky contacts on both GaN and AlGaN based devices. In order to allow harsh operating PD conditions, Cr/Au contacts were compared with W Schottky contacts. Related PD responsivities of up to 370 AAV were measured. In this way, noticeable improvements of device performances were also achieved, with responsivities enhanced by more than one order of magnitude.