A balanced-lattice-ledge nucleant having ledge inducing local densification of proteins and a balanced-lattice inducing self-organized crystal packing. Using this balanced-lattice-ledge nucleant enhances nucleation of protein crystals.

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Ga.sub.x1Al.sub.y1In.sub.1-x1-y1N (0≦x1≦1, 0≦x1+y1≦1) and the seed crystal is expressed as Ga.sub.x2Al.sub.y2In.sub.1-x2-y2N (0≦x2≦1, 0≦x2+y2≦1). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.

In a gallium arsenide crystal body, an etching pit density of the gallium arsenide crystal body is more than or equal to 10 cm.sup.2 and less than or equal to 10000 cm.sup.2, and an oxygen concentration of the gallium arsenide crystal body is less than 7.010.sup.15 atoms.Math.cm.sup.3. In a gallium arsenide crystal substrate, an etching pit density of the gallium arsenide crystal substrate is more than or equal to 10 cm.sup.2 and less than or equal to 10000 cm.sup.2, and an oxygen concentration of the gallium arsenide crystal substrate is less than 7.010.sup.15 atoms.Math.cm.sup.3.