ZnSe homoepitaxial MSM photodetectors with transparent ITO contact electrodes

Abstract

Determination of deep ultrathin equivalent oxide thickness (EOT) from measuring flat-band C-V curve," IEEE Trans. Electron Devices, vol. 49, no. 4, pp. 695-698, Apr. 2002. [6] M.-J. Jeng and J.-G. Hwu, "Thin-gate oxides prepared by pure water anodization followed by rapid thermal densification," IEEE Electron DeAbstract-We report the homoepitaxial growth of ZnSe layers on ZnSe substrates by molecular beam epitaxy (MBE). It was found that we can only observe an extremely strong ZnSe (004) x-ray peak with a full-width-athalf-maximum of 21.5 arcsec, which is much smaller than that observed from ZnSe grown on GaAs substrates. Photoluminescence and Hall measurement also indicate that the quality of our homoepitaxial ZnSe layers is good. ZnSe-based homoepitaxial metal-semiconductor-metal photodetectors with transparent indium-tin-oxide (ITO) contact electrodes were also fabricated. It was found that although ITO transparent contact electrodes can result in large photon absorption and large photocurrents, the low Schottky barrier height between ITO and homoepitaxial ZnSe would also result in relatively large dark currents. With an incident wavelength of 450 nm and a 1-V applied bias, it was found that the maximum responsivity is about 0.13 A/W, which corresponds to a quantum efficiency of 35%. Furthermore, it was found that the detector responsivity drops by more than two orders of magnitude across the cutoff region. Index Terms-Homoepitaxy, ITO, metal-semiconductor-metal (MSM) photodetector, molecular beam epitaxy (MBE), ZnSe.Short-wavelength blue and ultraviolet (UV) photodetectors are important devices that can be used in various commercial and military applications [1], [2]. For example, these blue/UV photodetectors can be used in space communications, ozone layer monitoring and flame detection. Currently, light detection in the blue/UV region still uses Si photodiodes. However, the most sensitive wavelength of Si photodiodes is not located in the blue/UV region, since room-temperature bandgap energy of Si is only 1.2 eV. Thus, the responsivity of Si photodiodes is low in the blue/UV region. With the advent of optoelectronic devices fabricated on wide direct bandgap materials, it becomes possible to produce high-performance solid-state photodetector arrays sensitive in the blue/UV region. For example, GaN-based photodetectors are already commercially available [3]. ZnSe is another wide direct bandgap material that is sensitive in the blue/UV region [4], [5]. Although various ZnSe-based blue/UV photodetectors were already been demonstrated, these ZnSe-based photodetectors were all grown on top of the closely lattice matched GaAs substrates. It is known that the slight lattice mismatch (0.27% at room temperature) between ZnSe and GaAs will still generate a huge amount of defects when we grow a very thick ZnSe epitaxial layer on top of the GaAs substrate [6]. The defects generated at the ZnSe-GaAs interface will significantly reduce the efficiency of the ZnSe-based photodetectors. One possible way to solve such a pr...

Construction of High-Quality P-Type ZnSe Nanowires/n-Type Si Heterojunctions and their Nano-Optoelectronic Applications

“…569 time less than 0.1 s, and the I light /I dark ratio is estimated to be 1.2× 10 3 . It should be noted that this value is much larger not only than that observed from a planar ZnSe homoepitaxial metal-semiconductor-metal photodetector [6], but aslo than the value of ~90 observed from ZnSe nanowire photodetector prepared on oxidized Silicon substrate [7]. In addition, the p-ZnSe NWs/n-Si heterojunction also exhibit perfect photovoltaic characteristics as well.…”

p-Cu2O-shell/n-TiO2-nanowire-core heterostucture photodiodes

“…They can be used for space communication, ozone layer monitoring, and flame detection [1]. In recent years, high-performance GaN-based (including AlGaN and AlInN) [2-5], ZnO-based [6], and ZnSe-based [7] photodetectors have all been demonstrated. However, high-quality GaN-based UV photodetectors could only be prepared on a sapphire substrate, which is much more expensive as compared with a glass substrate.…”