Preparation and Characterization of Wurtzitic GaN Single Crystals in Nano and Micro Scale
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National Laboratory of Super Hard Materials, Jilin University, Changchun 130023, P.R. China, [email protected] ABSTRACT Gallium nitride and its alloys are the most promising materials for short wave light emitters. If high quality GaN single crystals can be prepared, the GaN base light emitters should be fabricated directly on the lattice-matched GaN substrate. In this work, GaN crystals in nano and micro scale with definite faces have been prepared by dc arc discharge using gallium and N2+NH 3 as starting materials. Transmission electron microscope, selected area diffraction, x-ray microanalysis of energy dispersive spectroscopy, and x-ray diffraction investigation of the as grown GaN crystals show that the well faceted crystals are single crystalline GaN in wurtzite structure having lattice constants ao=3. I 8A and co=5.18A. The crystal size of stoichoimetric GaN in wurtzite structure depends on the partial pressure of nitrogen in the plasma. The maximum crystal size in this work is about several micrometers. INTRODUCTION Gallium nitride is a III-V group direct gap semiconductor with enormous potentials for optoelectronic devices from the blue to the near ultraviolet wavelengths which are presently inaccessible to semiconductor technology. GaN and its In and Al alloys span most of the visible region and extend well into the ultraviolet wavelengths[ 1]. The fabrication of high-quality single crystal GaN has been a formidable challenge to researchers to date[2]. In order to produce GaN, it has been experimentally realized that high temperature, activated nitrogen species and/or high nitrogen pressures are necessary to overcome the large kinetic barriers of formation. For this reason, conventional bulk and thin film growth technologies which are commonly used to produce III-V group semiconductors such as GaAs, and InP can not all be directly transferred to GaN production. Standard bulk growth technologies are not practical alternatives for the growth of GaN because experimental technologies have not been developed which can contain the high nitrogen pressure at the melt temperature. Refractory nitrides such as InN, GaN, and AIN, their solid solutions, and heterojunctions between them are one of the most promising families of electronic materials. All three are direct-band-gap semiconductors with their energy gaps covering the region from 1.95eV(InN) and 3.4eV(GaN) to 6.28eV(A1N). Thus, the growth of high quality crystals of these materials should lead to applications in optoelectronic devices from the visible to the ultraviolet part of the electromagnetic spectrum, as well as for high-power and high-temperature electronics[2,3]. GaN, in particular, was predicted to be the most promising materials for optoelectronic devices. GaN films have been grown using many growth technologies, including chemical vapor deposition(CVD)[4], metal-organic chemical vapor deposition(MOCVD)[5], molecular beam epitaxy(MBE)[6], and the plasma assisted processes[7,8] on a variety of substrates, such as silicon, spinel, silicon ca
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