Dark Current Reduction in ZnO-Based MSM Photodetectors with Interfacial Thin Oxide Layer
ABSTRACT In this paper the current transport mechanism of ZnO-based metal-semiconductor-metal ultraviolet photodetectors with various contact electrodes is discussed and simulated. The simulation is based on the thermionic emission theory and tunneling effects. It was found that the lowest dark current attributes to the Ru contact electrode. Moreover, it is shown that in order to achieve a large Schottky barrier height on ZnO and more reduction of dark current, one can insert a thin oxide layer between contacts and ZnO layer. The influence of the thickness of the insulator layer on the dark current of the MIS photodetector has also analyzed.
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ABSTRACT: Indium-tin-oxide (ITO), Au, Ni, and Pt layers were deposited onto n-GaN films and/or glass substrates by electron-beam evaporation. With proper annealing, it was found that we could improve the optical properties of the ITO layers and achieve a maximum transmittance of 98% at 360 nm. GaN-based MSM UV sensors with ITO, Au, Ni, and Pt as contact electrodes were also fabricated. It was found that we could achieve a maximum 0.12 A photocurrent and a photocurrent to dark current contrast higher than five orders of magnitude for the 600°C-annealed ITO/n-GaN MSM UV sensor at a 5-V bias voltage. We also found that the maximum responsivity at 345 nm was 7.2 A/W and 0.9 A/W when the 600°C-annealed ITO/n-GaN MSM UV sensor was biased at 5 V and 0.5 V, respectively. These values were much larger than those observed from other metal/n-GaN MSM UV sensors. However, the existence of photoconductive gain in the 600°C-annealed ITO/n-GaN MSM UV sensor also results in a slower operation speed and a smaller 3-dB bandwidth as compared with the metal/n-GaN MSM UV sensors.IEEE Sensors Journal 09/2002; · 1.48 Impact Factor
Article: ZnO-based MIS photodetectors[Show abstract] [Hide abstract]
ABSTRACT: We report the fabrication of ZnO-based metal–insulator–semiconductor (MIS) and metal–semiconductor–metal (MSM) photodetectors. With 5 V applied bias, it was found that photocurrent to dark current contrast ratios of the ZnO MSM and MIS photodetectors were 2.9 × 10 2 and 3.2 × 10 4 , respectively. It was also found that measured responsivities were 0.089 and 0.0083 A/W for the ZnO MSM and MIS photodetectors, respectively, when the incident light wavelength was 370 nm. Furthermore, it was found that ultraviolet (UV) to visible rejection ratios for the fabricated ZnO MSM and MIS photodetectors were 2.4 × 10 2 and 3.8 × 10 3 , respectively.66.Hf. 01/2007; 7860(85).
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ABSTRACT: ZnO epitaxial films were grown on sapphire substrates by molecular beam epitaxy. Schottky diodes and metal–semiconductor–metal (MSM) photodetectors with ruthenium (Ru) electrodes were also fabricated. It was found that Schottky barrier height at the Ru/ZnO interface was 0.76eV. It was also found that we achieved a photocurrent to dark current contrast ratio of 225 from our ZnO MSM photodetectors. Furthermore, it was found that the time constant of our photodetectors was 13ms with three-order decay exponential function.Journal of Crystal Growth 01/2005; 281(2):513-517. · 1.55 Impact Factor