Selective UV photodetectors based on the metal–AlGaN Schottky barrier

Abstract

Selective metal–AlGaN photodetectors based on the Schottky barrier and operating in UV spectral range have been developed. The selective photodiodes based on Ag–AlGaN Schottky barriers of different composition have been manufactured, which has made it possible to improve the photosensitivity in the UV spectral range and eliminate spurious signals in the long-wavelength part of the UV spectral range. This has made it possible to develop visible-blind photodetectors with the long-wavelength edge of photosensitivity lying at the wavelengths less than 350 nm. The width of the photosensitivity spectrum is within 15–40 nm, depending on the thickness of the Ag layer, which varies from 15 to 150 nm. The proper choice of the composition of the Al_xGa_1–xN solid solution ensures increase in the photoresponse and reduction of the FWHM spectrum width up to 11 nm by matching peaks of the Ag transmission spectrum and the absorption spectrum of the epitaxial layer. The sensitivity is 0.071 A/W. The combination of effects of wideband window and overthe- barrier transfer has made it possible to create the ultraselective UV photodetectors based on Au–AlGaN structures with a half-width of the photosensitivity spectrum of 5–6 nm for the wave range 350—375 nm and a sensitivity of up to 140 mA/W. Based on a structure with the upper Al_xGa_1–xN epitaxial layer (with the AlN content x = 0.1 or x = 0.06), selective photodetectors with the maximum photosensitivity at wavelengths of 355 nm and 362 nm have been developed. Application of an additional less wideband GaN layer has made it possible to independently control the short-wavelength and long-wavelength boundaries of the sensitivity range.