AlGaN/GaN heterostructures for UV photodetector applications

Metalorganic vapour phase epitaxy (MOVPE) process parameters of Al _xGa_1-xN (0<x<0.3) layers grown on c-oriented sapphire substrates were optimised from the point of view of their application in photoconductive and MSM type photodetectors. The low temperature AlN was used as a nucleation layer. The layers´ electrical properties were determined by C-V measurements performed in the range 5 Hz-13 MHz with a HP 4192A impedance meter using a mercury probe. The optical characterisation of Al_xGa_1-xN was performed by photoluminescence measurement at liquid He and room temperature. The aluminium mole fraction in the layers was determined and compared to the results derived from X-ray diffraction measurements. The photoconductive detectors were fabricated with Ti/Al/Ni/Au ohmic contacts. The I-V characteristics were taken and the photoresponse of the detectors was measured