Gallium oxide crystal manufacturing device
A gallium oxide crystal manufacturing device includes a crucible to hold a gallium oxide source material therein, a crucible support that supports the crucible from below, a crucible support shaft that is connected to the crucible support from below and vertically movably supports the crucible and the crucible support, a tubular furnace core tube that surrounds the crucible, the crucible support and the crucible support shaft, a tubular furnace inner tube that surrounds the furnace core tube, and a resistive heating element including a heat-generating portion placed in a space between the furnace core tube and the furnace inner tube. Melting points of the furnace core tube and the furnace inner tube are not less than 1900° C. A thermal conductivity of a portion of the furnace core tube located directly next to the crucible in a radial direction thereof is higher than a thermal conductivity of the furnace inner tube.
1. A gallium oxide crystal manufacturing device, comprising:
a crucible to hold a gallium oxide source material therein;
a crucible support that supports the crucible from below;
a crucible support shaft that is connected to the crucible support from below and vertically movably supports the crucible and the crucible support;
a tubular furnace core tube that surrounds the crucible, the crucible support and the crucible support shaft;
a tubular furnace inner tube that surrounds the furnace core tube; and
a resistive heating element comprising a heat-generating portion placed in a space between the furnace core tube and the furnace inner tube,
wherein melting points of the furnace core tube and the furnace inner tube are not less than 1900° C.,
wherein a thermal conductivity of a portion of the furnace core tube located directly next to the crucible in a radial direction of the furnace core tube is higher than a thermal conductivity of the furnace inner tube, and
wherein the furnace core tube comprises a first portion including the portion located directly next to the crucible in the radial direction of the furnace core tube and a second portion other than the first portion, and a thermal conductivity of the first portion is higher than a thermal conductivity of the second portion.
2. The gallium oxide crystal manufacturing device according to claim 1 , comprising:
a plate-shaped member that covers an opening at an upper end of the furnace core tube; and
a heat-retention material placed on the plate-shaped member.
3. The gallium oxide crystal manufacturing device according to claim 1 , wherein the portion of the furnace core tube located directly next to the crucible in the radial direction of the furnace core tube comprises an alumina-based ceramic or a magnesia-based ceramic, and the furnace inner tube comprises a zirconia-based ceramic.
4. The gallium oxide crystal manufacturing device according to claim 1 , wherein the crucible comprises a platinum-based alloy.
5. The gallium oxide crystal manufacturing device according to claim 4 , wherein the crucible support comprises a first block as the uppermost portion comprising a zirconia-based ceramic and directly in contact with the crucible, and a second block located under the first block, comprising an alumina-based ceramic and not in contact with the crucible.
6. The gallium oxide crystal manufacturing device according to claim 1 , wherein the furnace inner tube is surrounded by a heat-retention layer from side, above and below, the heat-retention layer is vertically separated into two sections, an upper heat-retention layer covering the upper side of the furnace inner tube and a lower heat-retention layer covering the lateral and lower sides of the furnace inner tube, the upper heat-retention layer and the lower heat-retention layer vertically sandwich a gap, and the gap is provided so as not to be horizontally continuous from the inside to the outside of the heat-retention layer.