Selectively-sensitive metal-semiconductor-metal photodetectors based on AlGaN/AlN and ZnCdS/GaP heterostructures

We report on the growth, fabrication and characterization of metal-semiconductor-metal (MSM) photodetectors based on AlGaN/AlN/Al2O3 and ZnCdS/ZnS/GaP heterostructures. The structures were grown by MOVPE at the temperatures 1050 oC and 415 oC respectively. Interdigital Au/Ni Schottky barrier contacts forming MSM-diode structures were deposited on the surfaces of AlGaN and ZnCdS. The finger width and gap were 3 µm and active diode area 100x100 µm2 thus suggesting short transittimes of photogenerated carriers, low capacitance of the diode structure and high-speed operation of the detectors. The spectral response of AlGaN MSM-diodes demonstrates the ability of detectors for true solar-blind response with maximum current responsivity ∼0.1 A/W at 230 nm under illumination from substrate. The I-V curves displayed dark currents of ∼50 pA at 40 V bias. The dark current of the ZnCdS diode is much lower (∼2 pA at 40 V), which confirms the high crystalline quality of the ZnCdS-layer (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)