Effect of halogen species of acidic mineralizer on solubility of GaN in supercritical ammonia

Determination of GaN solubility in supercritical ammonia with NH4F and NH4Cl mineralizer by in situ x-ray imaging of crystal dissolution

“…6) as reported by Ehrentraut et al for NH 4 Cl [11]; however, our solubility values with NH 4 F mineralizer are about two orders of magnitude lower. Taking into account that the solubility of GaN was reported to be similar in magnitude using NH 4 I, NH 4 Br and NH 4 Cl mineralizer by Tomida et al [12], a difference between the acidic mineralizers NH 4 F and NH 4 Cl of orders of magnitude is unexpected. From a first experiment with NH 4 Cl (2.5 mol%), we deduced a solubility of 0.05 mol GaN/mol NH 4 Cl at 550 1C and 1400 bar which is in the same order of magnitude as our corresponding solubility values for NH 4 F. Ehrentraut et al [11] reported a two orders of magnitude higher solubility of about 2.2 mol GaN/mol NH 4 Cl using a similar molar ratio of mineralizer and ammonia of 0.032 (in our experiment: 0.025).…”

“…To date, only few quantitative data on the solubility of GaN have been reported for selective process conditions [4,[10][11][12]. Additionally, all of the reported quantitative data (for ammonoacidic mineralizers: NH 4 Cl [10][11][12], NH 4 Br [12] and NH 4 I [12]) have been obtained by gravimetric investigation of residual reactants after dissolution experiments, i.e., by ex situ methods.…”

“…To date, only few quantitative data on the solubility of GaN have been reported for selective process conditions [4,[10][11][12]. Additionally, all of the reported quantitative data (for ammonoacidic mineralizers: NH 4 Cl [10][11][12], NH 4 Br [12] and NH 4 I [12]) have been obtained by gravimetric investigation of residual reactants after dissolution experiments, i.e., by ex situ methods. No investigations of GaN solubility with NH 4 F as mineralizer have so far been reported although it shows promising properties: NH 4 F offers a negative temperature gradient of solubility observed at temperatures of 550-650 1C [13], growth in polar, semipolar as well as nonpolar directions [13,14], high growth rates and good crystal quality [13,14].…”

Development of a novel in situ monitoring technology for ammonothermal reactors

“…The recent years, however, have seen an enormous progress in the field of ammonothermal growth of gallium nitride single crystals [1][2][3]. Owing to the extreme reaction conditions, only indirect methods for the determination of equilibrium and solubility data could be applied [1,[3][4][5][6][7]. The knowledge of the solubility in particular is an important prerequisite to control any solvothermal process at optimal operating conditions.…”

Heat and Fluid Flow in Solvothermal Autoclave for Single-Crystal Growth Process

“…Furthermore, in the numerical study, we had to clarify the conditions of temperature and flow fields. Tomida et al measured the solubility of GaN in supercritical ammonia and the corresponding growth rate (5) (6) and suggested that NH 4 I as an acid mineralizer could increase the crystal growth rate (6) . However, they did not report the temperature and flow fields of the autoclave.…”