Gallium nitride crystal growth method, gallium nitride crystal substrate, epi-wafer manufacturing method, and epi-wafer

A method of growing silicon-doped gallium nitride crystal by HVPE, the growth method comprising:

• (a) preparing carrier gasses for carrying gallium nitride precursors and for carrying a doping gas;
• (b) preparing as the doping gas a gas containing dopant silicon;
• (c) passing the prepared carrier gasses across a molecular film to purify them so that the carrier gasses have a dew point of not greater than −60° C.;
• (d) preparing a gallium source and an undersubstrate suitable for gallium nitride growth and placing the gallium source and the undersubstrate within an HVPE reactor;
• (e) via the carrier gasses supplying, at a predetermined total partial pressure, the gallium nitride precursors into the HVPE reactor, and thereby to the gallium source, and supplying the doping gas into the HVPE reactor, and heating the HVPE reactor interior to vapor-phase epitaxially grow gallium nitride crystal onto the undersubstrate;
• (f) growing the gallium nitride crystal to a thickness of at least 200 μm;
• and
• (g) repeating (a) through (f) a plurality of times to yield a production run of silicon-doped gallium nitride crystals, wherein
• said total partial pressure of the carrier gasses is predetermined together with said carrier-gas dew point in such a way as to impart to the grown gallium nitride crystal a silicon dopant concentration of not less than 2.2×1018 cm−3 correlating to a cracking frequency of not greater than 7% in the production run, given that an occurrence of cracking is taken to be 30 or more crack lines of 100 μm or greater length appearing over the entirety of a 45.8 mm-diameter area of each of the crystals grown in the production run.