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Vertically well-aligned ZnO nanowire ultraviolet ͑UV͒ photodetectors were fabricated by spin-on-glass technology on ZnO:Ga/glass templates. With 2 V applied bias, it was found that dark current density of the fabricated device was only 2.0ϫ 10 −7 A/cm 2 . It was also found that UV-to-visible rejection ratio and quantum efficiency of the fabricated ZnO nanowire photodetectors were more than 1000 and 12.6%, respectively.

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The characterizations of n-type doped GaN, p-type doped GaN and n-type doped In0.2Ga0.8N Schottky metal-semiconductor-metal (MSM) photodetectors were reported. The epilayers were grown on sapphire by metalorganic chemical vapor deposition (MOVCD). Schottky contacts were fabricated using Au, Ti, Ni and Pt metals. The dark and illuminated current–voltage characteristics of GaN and InGaN MSM photodetectors with different Schottky metals were studied. The n-GaN MSM photodetectors with Au Schottky contacts showed better responsivity than those with other metals and they were also better than Au/p-GaN and Ti/n-In0.2Ga0.8N MSMs. The effects of the pitch width between the interdigitate fingers and the thickness of Schottky metals on the characteristics of photocurrents were also studied.

Sputtering indium tin oxide (ITO) and e-beam ITO films deposited onto GaN as transparent electrodes for applications in metal–semiconductor–metal (MSM) photodetectors were fabricated and reported. The transmittances of 1000 Å-thick sputtering-ITO and e-beam ITO films were 78% and 67%, respectively, at a wavelength of 350 nm. The variation in the transmittance of the sputtering ITO films was not dependent on film thickness. The estimated effective barrier heights of the sputtering ITO and e-beam ITO films to GaN were 0.46 and 0.95 eV, respectively. This difference in barrier height originates from the formation of InGaN at the interface of ITO/GaN. Finally, GaN MSM photodetectors were fabricated using e-beam ITO electrodes. The peak responsivity of these e-beam ITO MSM photodetectors was 0.11 A/W at a 3 V bias. For a given bandwidth of 500 Hz, the corresponding noise equivalent power (NEP) and normalized detectivity D * were calculated to be 1.51×10-10 W and 2.96×109 cmHz0.5W-1, respectively.