PYROLYTIC BORON NITRIDE VESSEL

PROBLEM TO BE SOLVED: To facilitate the control of the internal temp. distribution of a pyrolytic boron nitride vessel used in the production of a compd. semiconductor signal crystal as well as to easily form a temp. gradient of molten starting material in the vessel by exposing a laminated cross section of pyrolytic boron nitride in a part of the inner surface of the vessel. SOLUTION: A laminated cross section of pyrolytic boron nitride is exposed in part of the inner surface of a pyrolytic boron nitride vessel for holding molten starting material used in the production of a compd. semiconductor single crystal. In the case where the compd. semiconductor single crystal is produced by LEC method, the central protruding part of the inner bottom of the vessel is removed by a prescribed thickness by mechanical polishing to exposed a laminated cross section in the part. The angle between the inner surface of the vessel and a laminated face in the laminated cross section exposed part (e.g. the angle θ25 at 25mm radius from the central axis of the vessel and the angle θ50 at 50mm radius) is preferably regulated to 0.5-90 deg..