Atmospheric pressure metalorganic vapor phase epitaxial growth and characterization of high quality GaN on sapphire (0001) substrates are reported. Using AlN buffer layers, GaN thin films with optically flat surfaces free from cracks are successfully grown. The narrowest x‐ray rocking curve from the (0006) plane is 2.70’ and from the (2024) plane is 1.86’. Photoluminescence spectra show strong near band edge emission. The growth condition dependence of crystalline quality is also studied.

Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer

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

Recent research results pertaining to InN, GaN and AlN are reviewed, focusing on the different growth techniques of Group III-nitride crystals and epitaxial films, heterostructures and devices. The chemical and thermal stability of epitaxial nitride films is discussed in relation to the problems of deposition processes and the advantages for applications in high-power and high-temperature devices. The development of growth methods like metalorganic chemical vapour deposition and plasma-induced molecular beam epitaxy has resulted in remarkable improvements in the structural, optical and electrical properties. New developments in precursor chemistry, plasma-based nitrogen sources, substrates, the growth of nucleation layers and selective growth are covered. Deposition conditions and methods used to grow alloys for optical bandgap and lattice engineering are introduced. The review is concluded with a description of recent Group III-nitride semiconductor devices such as bright blue and white light-emitting diodes, the first blue-emitting laser, high-power transistors, and a discussion of further applications in surface acoustic wave devices and sensors.

https://iopscience.iop.org/article/10.1088/0022-3727/31/20/001/pdf

Growth and applications of Group III-nitrides

Low-resistivity p-type GaN films were obtained by N2-ambient thermal annealing at temperatures above 700°C for the first time. Before thermal annealing, the resistivity of Mg-doped GaN films was approximately 1×106 Ωcm. After thermal annealing at temperatures above 700°C, the resistivity, hole carrier concentration and hole mobility became 2 Ωcm, 3×1017/cm3 and 10 cm2/Vs, respectively. In photoluminescence measurements, the intensity of 750-nm deep-level emissions (DL emissions) sharply decreased upon thermal annealing at temperatures above 700°C, as did the change in resistivity, and 450-nm blue emissions showed maximum intensity at approximately 700°C of thermal annealing.

https://iopscience.iop.org/article/10.1143/JJAP.31.L139/pdf

Thermal Annealing Effects on P-Type Mg-Doped GaN Films

Progress and prospects of group-III nitride semiconductors

The growth of single‐crystal epitaxial layers of onto (0001) oriented sapphire substrates from the liquid phase is shown to require three conditions:(i) the partial pressure of in the H2 ambient, greater than the equilibrium pressure, (ii) the growth melt positioned in a thermal gradient to transport the dissolved to the growth interface, and (iii) the control of nucleation by the addition of Bi to the growth melt. Studies of growth at temperatures from 850° to 1050°C show that the layer thickness, , is approximately linear in time and varies with growth temperature and atom fraction of Ga, in the growth melt. When , internal cracks in the basal plane hexagonal directions develop at the layer‐substrate interface and for they propagate to the surface and are thermally etched. A description is given of the interaction of liquid Ga with as a function of and . The low solubility of in Ga ( fraction at 1150°C) prevents useful growth by slow cooling of the melt. The inability to change the electron concentration, , with Zn doping and the decrease of with in the growth melt support but do not unambiguously confirm the model that the native donor is a nitrogen vacancy

Heteroepitaxial Thermal Gradient Solution Growth of GaN

The equilibrium pressures of N2 over and Ga are not known. Values of the heat and entropy of formation of are proposed that give equilibrium N2 pressures as a function of temperature. Experiments reported in the literature lead to consistent upper and lower bounds to the calculated curve but do not define its position very well. We report the results of three different types of experiments, using in H2, which tighten the bounds to the equilibrium curve: the pressures at which could be seen to form from Ga were upper limits; the pressure of in the exiting gas stream after reaction with Ga gives a qualified upper limit; and of greatest importance, we believe, are the measurements of the pressures generated when H2 is passed over . These latter pressures are lower limits to the equilibrium curve and are believed to lie close to it. The experimental results are in agreement with the calculated equilibrium pressures of N2 over GaN and Ga obtained using the heat of formation of based on the measurements of Hahn and Juza, and Mah and the assumption that the entropy and heat capacity of are the same as those of .

https://iopscience.iop.org/article/10.1149/1.2404274/pdf

R. A. Logan

Papers

Heteroepitaxial Thermal Gradient Solution Growth of GaN

The Equilibrium Pressure of N2 over GaN