Crystal of nitride of group-13 metal on periodic table, and method for producing the same

A method for producing a GaN crystal, the method comprising:

• (i) growing a tabular GaN crystal on a seed crystal from a linear opening in a <000-1> direction by an ammonothermal method in the presence of a mineralizer containing fluorine and iodine in such a manner that a main plane orientation of the tabular GaN crystal is different from a main plane orientation of the seed crystal, and
• (ii) growing the GaN crystal on the tabular GaN crystal,
• wherein
• the seed crystal is a GaN substrate having a (000-1) plane as the main plane;
• and
• the (000-1) plane surface is partially covered with a growth-inhibiting material to provide the linear opening where the (000-1) plane surface is not covered with the growth-inhibiting material.