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We report a novel approach for metal organic vapor phase epitaxy of (Al)GaN heterostructures on Si substrates. An approximately 90-100 nm thick SiC buffer layer is synthesized using the reaction between Si substrate and CO gas. High-resolution transmission electron microscopy reveals sharp crystalline interfaces with epitaxial relationship between SiC/Si and AlN/SiC layers. Optimization of SiC morphology and AlN seed layer thickness facilitates the growth of GaN layers free of pits (v-defects). It is also found that Si doping eliminates these defects in the case of growth on SiC templates with non-optimized surface morphology. Thus, synthesis of thin SiC buffer layer is suggested as a solution for the interface problems at the initial stage of III-N on Si epitaxy. [ABSTRACT FROM AUTHOR]

GaN is demonstrated to be an ideal anode for Li-ion batteries (LIBs) for the first time. Amorphous GaN@Cu nanorods (a-GaN@Cu) freestanding electrode is designed via a low-temperature pulsed laser deposition method, which exhibits prominent rate capability and untralong lifespan as an anode for LIBs. With porous interconnected metal nanorods substrate to improve the structure integrity and electronic conductivity, the a-GaN@Cu electrode delivers a capacity recovery of 980 mAh g−1 after 150 cycles from 0.25 to 6.25 A g−1 and a high discharge capacity of 509 mAh g−1 after 3000 cycles at 10.0 A g−1. The lithium storage in the a-GaN is also systematically studied, which suggests a redox reaction mechanism. [ABSTRACT FROM AUTHOR]

In recent years, different power transistors have been developed in silicon carbide (SiC) and gallium nitride (GaN) as replacements for silicon based IGBTs. This paper presents a simulation comparison of the static and dynamic performance of silicon IGBTs with different SiC and GaN based lateral and vertical power transistors (HEMT, MOSFET and IGBT) with breakdown voltage ratings between 1.2 kV to 15 kV. The strengths and weaknesses of different technologies which make them suitable at different voltage levels have been discussed. [ABSTRACT FROM AUTHOR]

Etching of gallium nitride for various device applications has attracted much attention; however, previous reports have all been performed in acidic or basic etchant solutions. Herein, we demonstrate how neutral electrolytes such as NaNO3 or NaCl can be used to rapidly etch n-GaN electrochemically and achieve a porous structure that is either vertically aligned or faceted according to the GaN crystallography, in NaNO3 and NaCl, respectively. It is demonstrated that the etching properties of NaNO3 and HNO3 are very similar, showing that the etching process in this system is surprisingly insensitive to pH. This neutral-pH process enables safer and greener GaN etching, as well as opening up the possibility of crystallographic etching of GaN using an anodic process. [ABSTRACT FROM AUTHOR]

Abstract: In this research, hexagonal wurtzite structure gallium nitride (GaN) thin film was grown on silicon (Si) substrate by using spin coating deposition method. Simple ethanol-based precursor with the addition of diethanolamine solution was used. High resolution X-ray diffraction results revealed that wurtzite structure GaN thin film with (002) preferred orientation was deposited on Si substrate. Flied-emission scanning electron microscopy and atomic force microscopy results showed that crack free GaN thin film with uniform and dense grains of GaN was formed. Finally, lattice vibrational characterization by p-polarized infrared reflectance technique revealed a strong reststrahlen feature of crystalline wurtzite GaN, and the transverse and longitudinal phonon modes of wurtzite GaN were clearly identified. [Copyright &y& Elsevier]

Abstract: Two kinds of novel GaN nanotowers on silicon (111) substrates by employing ultrathin Ni catalyst films (0.2nm) were successfully synthesized at different growth temperatures using a metal–organic chemical vapor deposition system. Scanning electron microscopy indicated that the density and growth direction of the nanotowers were highly sensitive to changes of growth temperature. The morphologies were characterized in detail, and showed triangular and hexagonal nanotowers which were oriented predominantly along and [0001] directions, respectively. Finally, a new growth mechanism is stated to explain the growth of these two novel GaN nanotowers. [Copyright &y& Elsevier]

Abstract: GaN synthesized by close space vapor transport in vacuum using GaN powder as the source material is reported. According to X-ray diffraction measurements, samples grown onto sapphire substrates are polycrystalline with the wurzite structure, while those grown onto fused silica substrates are amorphous. Scanning electron microscope and energy dispersive spectroscopy results show that the surface of the samples is composed of rounded droplets of GaN. Room temperature photoluminescence shows near band-edge emission and a broad defect band. Possible mechanisms allowing the deposition of GaN from the vapors of GaN powder are discussed. [Copyright &y& Elsevier]

Gallium nitride materials are at the forefront of nanoelectronic research due to their importance for UV optoelectronics. In this contribution, we present a facile and well-controlled synthesis of GaN nanodisks by rapid thermal ammonolysis of complex gallium fluoride precursor. We observed the formation of GaN nanodisks in 150 s at 800 °C. The structural properties of GaN were investigated by X-ray diffraction, Raman spectroscopy, and micro-photoluminescence. The morphology of GaN was investigated by scanning electron microscopy and the magnetic properties by superconducting quantum interference device (SQUID) techniques. The morphology of nanodisks was strongly influenced by the temperature of synthesis. The structure characterization shows a high concentration of defects related mainly to the vacancies of N and Ga. The magnetic measurement by SQUID shows paramagnetic behavior induced by structure defects. These findings have a strong implication on the construction of modern optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: Gallium nitride (GaN) powder was synthesized by the cyanonitridation of β-gallium oxide (β-Ga2O3) powder and characterized by powder X-ray diffraction, 71Ga magic-angle spinning nuclear magnetic resonance spectroscopy, Raman spectroscopy, and scanning electron microscopy. The cyano radical, which was formed by the thermal decomposition of organic compounds such as acetonitrile and melamine, was involved in the nitridation of β-Ga2O3. The formation of GaN via cyanonitridation commenced at slightly higher temperature than that via ammonolysis. The produced GaN powders showed five first-order phonon modes in Raman spectra. Particles’ morphologies were maintained during cyanonitridation, indicating that the β-Ga2O3 did not convert to GaN through gaseous species such as Ga2O. [Copyright &y& Elsevier]

Low thermal resistance GaN-on-diamond wafers offer enhanced thermal management with respect to GaN-on-SiC devices. The GaN/diamond interfacial thermal resistance can contribute significantly to the total device thermal resistance and must therefore be minimized to gain the maximum benefit from GaN-on-diamond. A contactless thermoreflectance measurement technique has been developed, which can be used after wafer growth and before device fabrication, enabling rapid feedback about the influence of growth parameters on interfacial thermal resistance. A measured \(2\times \) reduction in the GaN/diamond interfacial resistance is achieved by reducing the dielectric thickness between the GaN and diamond from 90 to 50 nm, enabling a potential 25% increase in transistor power dissipation for GaN-on-diamond. [ABSTRACT FROM AUTHOR]

A GaN MIS-HEMT with nitrogen (N)-passivation for power device applications is demonstrated. In this letter, nitrogen radicals were adopted to recover nitrogen-vacancy-related defects which were formed due to the thermal decomposition and evaporation of nitrogen atoms from GaN surface during high-temperature process. Besides, nitrogen radicals can also remove impurities and reduce surface dangling bonds by forming Ga-N bonds on the SiN/GaN interface. With N-passivation, the device shows high ON/OFF current ratio, steep subthreshold slope, low OFF-state leakage current, high breakdown voltage, and improved dynamic ON-resistance. The device reliability under high-electric field stress was also improved as a result. [ABSTRACT FROM AUTHOR]