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)