AlN formation by an Al/GaN substitution reaction

Abstract

Aluminium nitride (Aln) is a promising semiconductor material for use as a substrate in high-power, high-frequency electronic and deep-ultraviolet optoelectronic devices. We study the feasibility of a novel Aln fabrication technique by using the Al/Gan substitution reaction method. the substitution method we propose here consists of an Al deposition process on a Gan substrate by a sputtering technique and heat treatment process. the substitution reaction (Al + Gan = Aln + Ga) is proceeded by heat treatment of the Al/Gan sample, which provides a low temperature, simple and easy process. C-axis-oriented Aln layers are formed at the Al/Gan interface after heat treatment of the Al/Gan samples at some conditions of 1473-1573 K for 0-3 h. A longer holding time leads to an increase in the thickness of the AlN layer. The growth rate of the AlN layer is controlled by the interdiffusion in the Aln layer. Aluminium nitride (AlN) is a promising semiconductor material for use as a substrate in high-power, highfrequency electronic and optoelectronic devices. It can be used as a substrate in AlGaN-based ultraviolet C (UV-C) optoelectronic devices owing to its wide bandgap (above 6 eV) 1 , UV transparency 2 , and close lattice constant with that of AlGaN 3. AlN can be grown in two forms: film and bulk. AlN films have been fabricated by various methods, such as metal-organic vapour-phase epitaxy (MOVPE) 4,5 , hydride vapour phase epitaxy (HVPE) 6,7 , pulsed laser deposition (PLD) 8,9 , molecular beam epitaxy (MBE) 10,11 , or sputtering 12,13 , to improve its crystalline quality, surface area, growth rate, or lower its processing temperature. Annealing techniques have been demonstrated to improve the crystalline quality of AlN films 14-16. To facilitate the further development of AlN crystal growth, several researchers have developed original and unconventional techniques. For example, the pyrolytic transportation method 17 , the liquid phase epitaxy (LPE) method using a Ga-Al binary solution 18 , Al-Sn flux growth 19 , AlN fabrication by using Al and Li 3 N solid sources 20 , and elementary-source vapour-phase epitaxy (EVPE) 21 have been demonstrated. In the pyrolytic transportation method 17 , α-Al 2 O 3 is used as an Al-source material, and it is heated at 2223 K to form Al 2 O gas in the nitrogen gas flow. The Al 2 O gas is transported to the growth zone to react with nitrogen gas at 2023 K on a sintered AlN plate for 30 h, which yields a rod-like AlN crystal (48-mm long). The advantages of this method are an economically friendly α-Al 2 O 3 source and good crystalline quality of AlN. Wu et al. 21 used metallic Al and nitrogen gas as source materials to grow an AlN crystal, which they called elementary-source vapour-phase epitaxy (EVPE). They grew the AlN with a growth rate of 18 μm/h under an optimum growth zone temperature of 1823 K. The advantages of this method are that it is conducted at a temperature lower than that of the sublimation method using no hazardous gas. Regarding the LPE methods, Adachi et al. 18 grew a 1-µm-...

Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles

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A Review of Light-Emitting Diodes and Ultraviolet Light-Emitting Diodes and Their Applications

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