EQUIPMENT AND METHOD FOR PRODUCING CRYSTAL BY VERTICAL BOAT METHOD

1 . An equipment for crystal growth by a vertical boat method, comprising:

a crucible enclosing a raw material;

an ampoule encapsulating the crucible; and

a crystal growth heater provided around the ampoule to heat the raw material,

wherein the raw material is melted into a raw material melt by the crystal growth heater and a temperature of the raw material melt is controlled such that a crystal grows in the crucible from a bottom toward a top thereof,

wherein the crucible encloses GaAs as the raw material and Si as a dopant,

wherein the ampoule comprises an additional B 2 O 3 as an additional raw material at a position separated from the raw material, and a B 2 O 3 adding-heater to heat the additional B 2 O 3 separately from the raw material, and

wherein a temperature of the additional B 2 O 3 is controlled by the B 2 O 3 adding-heater during growth of the crystal such that at least a portion of the additional B 2 O 3 is melted and supplied into the crucible.

2 . The equipment according to claim 1 , wherein the ampoule further comprises an additional B 2 O 3 container at an upper portion of the crucible to enclose the additional B 2 O 3 , and

wherein the additional B 2 O 3 container comprises an adding port formed at a bottom thereof through which the additional B 2 O 3 is supplied into the crucible.

3 . The equipment according to claim 2 , wherein the adding port is formed at a position off a central axis of the crucible.

4 . The equipment according to claim 2 , wherein the adding port is lidded by a lid of another material having a higher melting point than the additional B 2 O 3 before the growth of the crystal, and

wherein the lid is melted by the B 2 O 3 adding-heater during the growth of the crystal such that the adding port is opened so as to supply the additional B 2 O 3 into the crucible.

5 . The equipment according to claim 4 , wherein the lid has a shape of a plate and is housed in the additional B 2 O 3 container so as to lid the adding port.

6 . The equipment according to claim 4 , wherein the lid has a shape of a bottle-stopper to fit to the adding port and is fitted to the adding port so as to lid the adding port.

7 . The equipment according to claim 2 , wherein the additional B 2 O 3 container comprises a bottom having a shape of a funnel.

8 . The equipment according to claim 2 , wherein the additional B 2 O 3 container comprises PBN.

9 . The equipment according to claim 2 , wherein the adding port has an inner diameter of 0.3 to 1 mm.

10 . The equipment according to claim 1 , wherein the crystal growth heater is separated from the B 2 O 3 adding-heater by a heat insulation material.

11 . The equipment according to claim 1 , wherein the B 2 O 3 adding-heater is disposed above the ampoule.

12 . The equipment according to claim 2 , wherein a heat-transfer material for induction heating is provided around the additional B 2 O 3 container.

13 . A method for crystal growth by a vertical boat method, comprising:

forming a raw material melt by melting a raw material held in a crucible; and

controlling a temperature of the raw material melt to grow a crystal in the crucible from the bottom toward the top thereof,

wherein GaAs as the raw material and Si as a dopant are held in the crucible,

wherein an additional B 2 O 3 as an additional raw material is held at a position separated from the raw material before the growth of the crystal, and

wherein a temperature of the additional B 2 O 3 is controlled during the growth of the crystal such that at least a portion of the additional B 2 O 3 is melted so as to be supplied into the crucible.