Polycrystalline aluminum nitride base material for crystal growth of GaN-base semiconductor and method for manufacturing GaN-base semiconductor using the same
There is provided a polycrystalline aluminum nitride substrate that is effective in growing a GaN crystal. The polycrystalline aluminum nitride base material for use as a substrate material for grain growth of GAN-base semiconductors, contains 1 to 10% by weight of a sintering aid component and has a thermal conductivity of not less than 150 W/m·K, the substrate having a surface free from recesses having a maximum diameter of more than 200 μm.
1. A polycrystalline aluminum nitride base material for use as a substrate material for grain growth of GaN-base semiconductors, the polycrystalline aluminum nitride base material containing 1 to 10% by weight of a sintering aid component and having a thermal conductivity of not less than 150 W/m·K, and the substrate having a surface free from recesses having a maximum diameter of more than 200 μm,
wherein the sintering aid component comprises one or more materials selected from the group consisting of rare earth elements, rare earth element oxides, and rare earth element-aluminum oxides,
the recesses are any one of pores, traces after dropping of AlN crystal grains, and traces after dropping of the sintering aid component,
the polycrystalline aluminum nitride base material comprises an aluminum nitride crystal and a grain boundary phase, grains of the aluminum nitride crystal having a mean diameter of not less than 1 μm and not more than 7 μm, and
the substrate surface has a skewness (R sk ) of +0.5 to −0.5, and
the substrate has a diameter of not less than 50 mm.
2. The polycrystalline aluminum nitride substrate according to claim 1 , wherein the maximum diameter of the recesses is not more than 50 μm.
3. The polycrystalline aluminum nitride base material according to claim 1 , wherein the substrate has a diameter of not less than 50 mm.
4. The polycrystalline aluminum nitride base material according to claim 1 , wherein the substrate surface has 0 (zero) or one recess having a maximum diameter of more than 20 μm per unit area of 1 inch×1 inch.
5. The polycrystalline aluminum nitride base material according to claim 1 , wherein 0 (zero) or one micropore having a maximum diameter of more than 0.5 μm is present per unit area of 10 μm×10 μm in the grain boundary phase on the surface of the substrate.
6. A method for manufacturing a GaN-base semiconductor, the method comprising growing a GaN-base semiconductor crystal using a polycrystalline aluminum nitride base material according to claim 1 .
7. The method for manufacturing a GaN-base semiconductor according to claim 6 , wherein the GaN-base semiconductor crystal is grown through a buffer layer.
8. The method for manufacturing a GaN-base semiconductor according to claim 6 , wherein the GaN-base semiconductor is one semiconductor selected from the group consisting of GaN, InGaN, AlGaN, and InAlGaN.
9. The polycrystalline aluminum nitride base material according to claim 1 , wherein the crystal growth face of the polycrystalline aluminum nitride substrate is disk, square or rectangular.
10. The polycrystalline aluminum nitride base material according to claim 1 , wherein the polycrystalline aluminum nitride substrate has a disk-shaped having a diameter of not less than 100 mm.