The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

The experimental study of InN and In-rich InGaN by a number of structural, optical and electrical methods is reviewed. Recent advances in thin film growth have produced single crystal epitaxial layers of InN which are similar in structural quality to GaN films made under similar conditions and which can have electron concentrations below 1 × 1018 cm−3 and mobilities exceeding 2000 cm2 (Vs)−1. Optical absorption, photoluminescence, photo-modulated reflectance and soft x-ray spectroscopy measurements were used to establish that the room temperature band gap of InN is 0.67 ± 0.05 eV. Experimental measurements of the electron effective mass in InN are presented and interpreted in terms of a non-parabolic conduction band caused by the k · p interaction across the narrow gap. Energetic particle irradiation is shown to be an effective method to control the electron concentration, n, in undoped InN. Optical studies of irradiated InN reveal a large Burstein–Moss shift of the absorption edge with increasing n. Fundamental studies of the energy levels of defects in InN and of electron transport are also reviewed. Finally, the current experimental evidence for p-type activity in Mg-doped InN is evaluated.

http://iopscience.iop.org/article/10.1088/0022-3727/39/5/R01/pdf

Structure and electronic properties of InN and In-rich group III-nitride alloys

In this study, we investigated phase separation and long-range atomic ordering phenomena in InGaN alloys produced by molecular beam epitaxy. Films grown at substrate temperatures of 700–750 °C with indium concentration higher than 35% showed phase separation, in good agreement with thermodynamic predictions for spinodal decomposition. Films grown at lower substrate temperatures (650–675 °C) revealed compositional inhomogeneity when the indium content was larger than 25%. These films, upon annealing to 725 °C, underwent phase separation, similar to those grown at the same temperature. The InGaN films also exhibited long-range atomic ordering. The ordering parameter was found to increase with the growth rate of the films, consistent with the notion that ordering is induced at the growth surface. The ordered phase was found to be stable up to annealing temperatures of 725 °C. A competition between ordering and phase separation has been observed, suggesting that the driving force for both phenomena is lattice...

Phase separation and ordering in InGaN alloys grown by molecular beam epitaxy

III-Nitride nanowire optoelectronics

We present the results of optical studies of the properties of InxGa1−xN epitaxial layers (0<x<0.2) grown by metalorganic chemical vapor deposition. The effects of alloying on the fundamental band gap of InxGa1−xN were investigated using a variety of spectroscopic techniques. The fundamental band-gap energies of the InxGa1−xN alloys were determined using photomodulation spectroscopy measurements and the variation of the fundamental band gap was measured as a function of temperature. The effects of pressure on the band gap for InxGa1−xN samples with different alloy concentrations were examined by studying the shift of photoluminescence (PL) emission lines using the diamond-anvil pressure-cell technique. The results show that PL originates from effective-mass conduction-band states. Anomalous temperature dependence of the PL peak shift and linewidth as well as the Stokes shift between photoreflectance and PL lines is explained by composition fluctuations in as-grown InGaN alloys.

Optical properties of InxGa1−xN alloys grown by metalorganic chemical vapor deposition

Compositional inhomogeneity in a GaInN ternary alloy layer is investigated A theoretical estimation of the interaction parameter based on the delta lattice parameter suggests that the immiscibility of InN in a nitride alloy is very strong We investigate the compositional splitting and the existence of InN inclusion in the GaInN epilayer grown on sapphire (0001) substrates The mechanism of compositional inhomogeneity is discussed

Xiao-Zhong Dang

Papers

Compositional inhomogeneity and immiscibility of a GaInN ternary alloy