Gallium nitride crystal substrate and method for manufacturing gallium nitride crystal substrate

A gallium nitride crystal substrate,

• the gallium nitride crystal substrate having a main surface whose closest low-index crystal plane is (0001), and
• containing carbon at a concentration of 2×1017 cm−3 or more and 3×1019 cm−3 or less,
• wherein a resistivity of the gallium nitride crystal substrate at a temperature of 20°C. is 1×108 Ωcm or more.

A method for manufacturing a gallium nitride crystal substrate, the method comprising:

• flowing hydrocarbon gas from a dopant gas line in a heated flow channel containing quartz, thereby forming a carbon coating on at least a part of an inner surface of a high temperature region of the flow channel, including at least a part of the dopant gas line;
• and
• epitaxially growing a crystal layer including carbon-containing gallium nitride crystal above a seed substrate by supplying gallium chloride gas, nitrogen source gas, and hydrocarbon gas to the seed substrate, which is heated, through the flow channel having the carbon coating formed on the inner surface thereof, by an HVPE method.