Ammonothermal and HVPE Bulk Growth of GaN

Prospective view of nitride material synthesis

“…The growth of GaN by the ammonothermal method has been the subject of intense research for nearly three decades and is well summarized in recent reviews. 19,24,26 The typical ammonothermal process set up is illustrated in Figure 2. 27 Some of the key takeaways from the accumulated literature are that (a) linear crystal growth rates are relatively slow, with top reported values of around 100-200 µm/day for ammonobasic 28 and up to 700 µm /day for ammonoacidic growth, 29 (b) dislocation densities can be quite low, down as far as 100 defects/cm 2 , 30 (c) oxygen is the key impurity, 19 (d) simultaneous growth in different crystal planes can be destabilizing, 31 and (e) very long growth times are a significant drag on the speed of process innovation.…”

“…19,24,26 The typical ammonothermal process set up is illustrated in Figure 2. 27 Some of the key takeaways from the accumulated literature are that (a) linear crystal growth rates are relatively slow, with top reported values of around 100-200 µm/day for ammonobasic 28 and up to 700 µm /day for ammonoacidic growth, 29 (b) dislocation densities can be quite low, down as far as 100 defects/cm 2 , 30 (c) oxygen is the key impurity, 19 (d) simultaneous growth in different crystal planes can be destabilizing, 31 and (e) very long growth times are a significant drag on the speed of process innovation. From the industrial perspective, it appears that crystal quality (especially optical clarity), lateral crystal size scaling, and yield are the primary limiting factors.…”

“…The growth of GaN by the ammonothermal method has been the subject of intense research for nearly three decades and is well summarized in recent reviews 19,24,26 . The typical ammonothermal process set up is illustrated in Figure 2 27 .…”

“…Gallium nitride can be grown by hydride vaporphase epitaxy (HVPE). 18,19 While the method is relatively straightforward and the linear growth rates are very attractive, some of the troublesome details of the crystal growth have prevented a market takeover by HVPE over foreign material substrates. For one, the natural facets of gallium nitride behave in a way to decrease the cross-section of the crystal under typical HVPE conditions.…”