Based on electronic structure and atomic size considerations, nitrogen has been regarded as the most suitable impurity for p-type doping in ZnO. However, numerous experimental efforts by many different groups have not resulted in stable and reproducible p-type material, casting doubt on the efficacy of nitrogen as a shallow acceptor. Based on advanced first-principles calculations we find that nitrogen is actually a deep acceptor, with an exceedingly high ionization energy of 1.3 eV, and hence cannot lead to hole conductivity in ZnO. In light of this result, we reexamine prior experiments on nitrogen doping of ZnO.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-001476.pdf

Why nitrogen cannot lead to p-type conductivity in ZnO

First‐principles electronic structure calculations on wurtzite AlN, GaN, and InN reveal crystal‐field splitting parameters ΔCF of −217, 42, and 41 meV, respectively, and spin–orbit splitting parameters Δ0 of 19, 13, and 1 meV, respectively. In the zinc blende structure ΔCF≡0 and Δ0 are 19, 15, and 6 meV, respectively. The unstrained AlN/GaN, GaN/InN, and AlN/InN valence band offsets for the wurtzite (zinc blende) materials are 0.81 (0.84), 0.48 (0.26), and 1.25 (1.04) eV, respectively. The trends in these spectroscopic quantities are discussed and recent experimental findings are analyzed in light of these predictions.

Valence band splittings and band offsets of AlN, GaN and InN.

This study reviews NiO film deposition using the Spray Pyrolysis Technique (SPT). Physical and chemical methods can be used to deposit NiO film. This review looks at different precursors and their characterization methods for spray deposition of NiO thin film. The usefulness of SPT emanates from this method being simple, low cost, and viable for mass production. It gives high product purity for metallic and non-metallic material deposition. Nickel chloride, nickel acetate, nickel nitrate, nickel hydroxide, nickel sulfate, and nickel formate are the major precursors for NiO thin film deposition. Nickel chloride and nickel acetate are the most used and highly available precursors. Unlike nickel acetate, nickel chloride precursors corrode the deposition equipment (spray gun). These precursors are relatively cheap compared to current materials used for solar panels (cells). SPT equipment consumes negligible power during deposition and none after usage. Various authors have investigated the physical, chemical, optical, structural characterization and properties of nanostructured NiO thin film. NiO films are p-type semiconductors and as such possesses direct band gap suitable for various applications. The film has been categorized as an excellent material for optoelectronic applications because of its tune-ability for optimization. The wide band gap is in the range of 3.25–4.0 eV. This review will be useful to researchers exploring solar photovoltaic potentials for solving electricity problems of developing countries.

Review of nanostructured NiO thin film deposition using the spray pyrolysis technique

Breakthroughs in NiOx-HTMs towards stable, low-cost and efficient perovskite solar cells

ZnO nanoparticles are still a hot area for research even after ample work has been done by researchers across the world. It is a versatile material for doping of different transition metals among o...

Progress on Transition Metal-Doped ZnO Nanoparticles and Its Application

Structures, electrical and optical properties of nickel oxide films by radio frequency magnetron sputtering

Undoped InN thin film was grown on p-GaN/Al2O3 (0001) template by molecular beam epitaxy. Near-infrared (NIR) electroluminescence (EL) that overlapped the optical communication wavelength range was realized using the n-InN/p-GaN heterojunction structure. The light emitting diode showed typical rectification characteristics with a turn-on voltage of around 0.8 V. A dominant narrow NIR emission peak was achieved from the InN side under applied forward bias. By comparing with the photoluminescence spectrum, the EL emission peak at 1573 nm was attributed to the band-edge emission of the InN film.

Near infrared electroluminescence from n-InN/p-GaN light-emitting diodes

Arsenic-doped ZnO (ZnO:As) films were grown by metal–organic chemical vapor deposition (MOCVD) on GaAs layers, which were deposited on sapphire substrates by sputtering using a GaAs target. The As doping was obtained by thermal diffusion. The ZnO:As films were annealed in nitrogen (ZnO:As:N2) and oxygen (ZnO:As:O2) atmosphere, respectively. X-ray photoelectron spectroscopy (XPS) measurements showed that annealing in oxygen facilitated even As doping in ZnO films and the content of As remains around 3.4% after Ar+ bombardment. However, annealing in N2 leads to the aliquation of As at the surface for ZnO:As films. Core level results show that there are two chemical states of As in ZnO:As:O2 films including AsZn–2VZn and AsZn, while four types exist in ZnO:As:N2 films including AsZn, AsZn–2VZn, Asi, and AsO. The contribution centered at around 43.9 eV of the As 3d peak is ascribed to AsZn–2VZn. The valence band maximum (VBM) spectrum taken by ultraviolet photoelectron spectroscopy (UPS) indicates that the Fermi energy of ZnO:As:O2 films shifts toward the VBM by 0.37 eV compared with undoped ZnO films, which proves AsZn–2VZn is an acceptor in ZnO:As:O2 films, but the ZnO:As films still show n-type conductivity, which is possibly due to the compensation of As-related donor and native defects. Detailed analysis of the chemical states of As may help point toward paths for growing high-quality ZnO:As films.

Study of arsenic doping ZnO thin films grown by metal–organic chemical vapor deposition via x-ray photoelectron spectroscopy

Growth and conduction mechanism of As-doped p-type ZnO thin films deposited by MOCVD

An n-InN nanodots/p-Si(1 1 1) heterojunction diode was fabricated by plasma-assisted molecular beam epitaxy. The device shows clear rectifying behaviour with a turn-on voltage of approximately 1.2 V at room temperature. The near-infrared electroluminescence (EL) can be observed under forward bias, which covers a wide wavelength range. In comparison with the photoluminescence spectra, the maximum of the EL spectra has a blueshift which is probably due to the size quantization effect of small-sized InN nanodots and their stronger contribution to the EL intensity. On the other hand, there is an obvious enhancement of the less dominant transitions on the short wavelength side of the EL spectra, which may arise from the recombination of the injected holes with the extremely high-density surface electrons of InN nanodots.

http://iopscience.iop.org/article/10.1088/0022-3727/45/21/215102/pdf

Fubin Gao

Papers

Structures, electrical and optical properties of nickel oxide films by radio frequency magnetron sputtering

Near infrared electroluminescence from n-InN/p-GaN light-emitting diodes

Study of arsenic doping ZnO thin films grown by metal–organic chemical vapor deposition via x-ray photoelectron spectroscopy

Growth and conduction mechanism of As-doped p-type ZnO thin films deposited by MOCVD

Near-infrared electroluminescence emission from an n-InN nanodots/p-Si heterojunction structure