The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.

Optical properties of ZnO nanostructures.

Transparent conductors as solar energy materials: A panoramic review

Zinc oxide (ZnO) is a wide band gap semiconductor with potential applications in optoelectronics, transparent electronics, and spintronics. The high efficiency of UV emission in this material could be harnessed in solid-state white lighting devices. The problem of defects, in particular, acceptor dopants, remains a key challenge. In this review, defects in ZnO are discussed, with an emphasis on the physical properties of point defects in bulk crystals. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. However, experiments and theory have shown that O vacancies are deep donors, while Zn interstitials are too mobile to be stable at room temperature. Group-III (B, Al, Ga, and In) and H impurities account for most of the n-type conductivity in ZnO samples. Interstitial H donors have been observed with IR spectroscopy, while substitutional H donors have been predicted from first-principles calculations but not observed directly. Despite numerous reports, reliable p-t...

Defects in ZnO

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Створення порталу інформаційно-довідкових ресурсів міністерства освіти і науки україни

F-doped and undoped ZnO nanocrystalline films were prepared from thermal oxidation of ZnF2 films deposited on a silica substrate by electron beam evaporation. The F-doped ZnO film has very low electrical resistivity of 7.95×10−4Ωcm and a high optical transmittance. The study also indicated that (1) the substitutional F atoms in the film serve as donors to increase the carrier concentration and the optical band gap with respect to undoped ZnO film, and (2) F passivation reduces the known number of Os2−/Os− surface states and increases carrier mobility.

F-doping effects on electrical and optical properties of ZnO nanocrystalline films

A series of MgxZn1−xO thin films has been prepared by metalorganic chemical vapor deposition and metal-semiconductor-metal structured ultraviolet photodetectors are fabricated from these films. The cutoff wavelengths of the photodetectors can cover the whole solar-blind spectrum range (220–280 nm) by varying Mg content in the MgxZn1−xO thin films. As a representative, the photodetector fabricated from Mg0.52Zn0.48O shows an ultraviolet/visible rejection ratio of about four orders of magnitude, and the dark current is 15 pA at 10 V bias. These results demonstrate that high-performance photodetectors operating in the whole solar-blind spectrum range can be realized in MgxZn1−xO films.

MgxZn1−xO-based photodetectors covering the whole solar-blind spectrum range

High Mg content mixed-phase Zn0.38Mg0.62O was deposited on a-face sapphire by plasma-assisted molecular beam epitaxy, based on which a metal-semiconductor-metal solar-blind ultraviolet (UV) photodetector was fabricated. The dark current is only 0.25 pA at 5 V, which is much lower than that of the reported mixed-phase ZnMgO photodetectors. More interestingly, different from the other mixed-phase ZnMgO photodetectors containing two photoresponse bands, this device shows only one response peak and its −3 dB cut-off wavelength is around 275 nm. At 10 V, the peak responsivity is as high as 1.664 A/W at 260 nm, corresponding to an internal gain of ∼8. The internal gain is mainly ascribed to the interface states at the grain boundaries acting as trapping centers of photogenerated holes. In view of the advantages of mixed-phase ZnMgO photodetectors over single-phase ZnMgO photodetectors, including easy fabrication, high responsivity, and low dark current, our findings are anticipated to pave a new way for the dev...

High-performance solar-blind ultraviolet photodetector based on mixed-phase ZnMgO thin film

Structure and photoluminescence of Mn-passivated nanocrystalline ZnO thin films

Undoped n-ZnO films have been deposited onto p-GaN to form a pn heterojunction, and the current−voltage curve of the heterojunction shows obvious rectifying behaviors. A photodetector is fabricated...

D.Z. Shen

Papers

F-doping effects on electrical and optical properties of ZnO nanocrystalline films

MgxZn1−xO-based photodetectors covering the whole solar-blind spectrum range

High-performance solar-blind ultraviolet photodetector based on mixed-phase ZnMgO thin film

Structure and photoluminescence of Mn-passivated nanocrystalline ZnO thin films

High Spectrum Selectivity Ultraviolet Photodetector Fabricated from an n-ZnO/p-GaN Heterojunction