Study of GaN solubility in ammonothermal alkaline solution

A set of research data related to article "Study of GaN solubility in ammonothermal alkaline solution"; Journal of Crystal Growth 647 (2024) 127864.The aim of this paper was to determine the solubility of gallium nitride (GaN) in supercritical ammonia with an alkaline mineralizer (NaNH₂) under basic ammonothermal conditions. The set contains the data used to create Figures 1-6.

Figure 1. Images in polarized light: examples of rectangular GaN samples with differently prepared surfaces selected for further dissolution processes: a) as-grown, b) as-cut, c) lapped d) optically flat; crosses on the (0001) surface (marked with a diamond blade pencil and surrounded by white circles) on the samples allowed to distinguish between (000–1) and (0001) surfaces.

Figure 2. a) scheme of ammonothermal autoclave with inner diameter of 14 mm as used for GaN solubility experiments: a – multiplier, b – heater, b) magnification of the autoclave reaction chamber: c – alarm thermocouple, d – Bridgman piston, e – holder with samples, f – autoclave, g – valve, h – control thermocouple.

Figure 3. Schematic of the pressure measurement setup in an autoclave: 1 – screw, 2 – oil pump, 3 – gauge, 4 – autoclave with multiplier, 5 – Bridgman piston. The rotation of the screw moves the piston of the oil pump connected to the multiplier, which causes the movement of the Bridgman piston. Changing the oil pressure changes the position of the Bridgman piston (up − p1 and down − p2).

Figure 4. Temperature dependence of dissolved GaN (from all the crystals in the autoclave in a given process) at constant values of NaNH₂ mineralizer concentration and pressure of 300 MPa after 1, 2, 4, 8, and 16 days of experiment. According to the law of propagation of measurement errors, the error bars were calculated and plotted on a graph for the ratio of dissolved GaN moles (nGaN) to NH₃ moles (nNH₃).

Figure 5. Comparison of dissolved GaN versus surface preparation of samples at different temperatures after 4 days, error bars ± 2 × 10^-4.

Figure 6. Images from optical microscope with Nomarski contrast for GaN samples before the dissolution, after the process at 300 ◦C and after the dissolution process at 550 ◦C with the following surface state: a) as-grown b) optically flat, c) as-cut and d) lapped.