Growth and characterization of a novel hyperspectral detector using the III-nitrides

We report on the growth and characterization of a novel; III-nitrides based, tunable hyperspectral photodetector. The proposed device structure consists of AlxGa1-xN multilayer heterostructure with At composition of 0 < x < 1 grown on, a GaN/sapphire template. The AlxGa1-xN heterostructure forms a stepped triangular profile potential barrier whereby the height of the potential barrier can be tuned by varying the applied voltage. Height of the potential barrier determines the threshold energy of the photoemission current over the potential barrier and hence determines the detection wavelength of the device, Device structures with different AlGaN layer thicknesses are evaluated to understand the dependence of the dark, current and the quantum efficiency of the device on the thickness' 1 of the, barrier structure. Internal photoemission (IPE) measurements have been carried out to measure the potential barrier faced by the photoexcited carriers. A reduction in potential barrier by 0.65 eV is observed over an applied voltage of 1.3 V, confirming the tunability of detection wavelength. Current-voltage (I-V) measurements and atomic force microscopy (AFM) have been used to study and improve the device performance. IPE, I-V and AFM results are presented I g with a discussion an the principle of device operation, along detection wavelength tunability range and device structure optimization parameters. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.