Fabrication of high-quality GaN substrates using the Na flux method

Abstract

Gallium nitride (GaN) substrates fabricated along the nonpolar and semipolar directions are the most promising materials for realizing optical and electronic devices with low power consumption. In this study, we carry out the Na flux growth on -plane GaN templates grown heteroepitaxially on sapphires. The GaN crystals are grown at low supersaturation using the Na flux method with the dipping technique. The crystallinity of the grown GaN crystals is improved compared to that of the seed substrates. Then it improves further by lowering the supersaturation. Finally, we succeed in fabricating a 2-in. -plane GaN single crystal with high transparency and crystallinity.

Computational fluid dynamics simulation study of the gas flow balance in a vertical HVPE reactor with a showerhead for low cost bulk GaN crystal growth

“…The most effective way to manufacture bulk GaN substrates at low costs is to slice them out from bulk GaN ingot. 13,14) Hydride vapor phase epitaxy (HVPE), [15][16][17] ammonothermal [18][19][20][21][22] and sodium flux [23][24][25][26][27] are the most popular methods for making bulk GaN crystals. HVPE is the most promising method among them owing to its relative high growth rate (>100 μm h −1 ) and its crystallization of high-purity material.…”

Mechanism and enhancement of anti-parasitic-reaction catalytic activity of tungsten-carbide-coated graphite components for the growth of bulk GaN crystals

“…Hydride vapor phase epitaxy [4][5][6][7][8][9][10] (HVPE) is a mainstream technique for supplying present commercial GaN wafers, in which the GaN crystal growth rate typically reaches ∼100 μm h −1 ; thus, HVPE can be referred to as a higher-rate GaN growth technique compared to other GaN growth techniques (metalorganic vapor phase epitaxy, 11,12) Na-flux, 13,14) and ammonothermal 15,16) ). Difficulties in achieving continuous long-duration HVPE-GaN growth are largely caused by "parasitic reactions"-in the case of HVPE-GaN growth, this denotes unintended polycrystal formation on hightemperature reactor components in the system.…”

Study on the stress and mechanism of self-separated GaN grown by Na-flux method

“…Due to the weakening of the chemical bonds around the dislocations of the GaN crystal, the crystals around this area are easily dissolved. 42,43) Therefore, in areas with high dislocation density, the dissolution rate of GaN crystal is faster, which will make the surface rough. When the GaN concentration reaches a supersaturated state, the GaN crystal starts to grow.…”