Group III nitride crystal, method for growing the group III nitride crystal, and apparatus for growing the same
When a group III nitride crystal is grown in a pressurized atmosphere of a nitrogen-containing gas from a melt 50 including at least a group III element, nitrogen and an alkali metal or an alkali earth metal, a melt-holding vessel 160 that holds the above-described melt 50 is swung about two axes different in direction from each other such as an X-axis and a Y-axis.
1. A method for growing a group III nitride crystal, the method comprising:
growing a group III nitride crystal in a pressurized atmosphere of a nitrogen-containing gas from a melt comprising at least a group III element, nitrogen and an alkali metal or an alkali earth metal; and
swinging a melt-holding vessel about two axes simultaneously, the melt-holding vessel holding, the melt,
wherein the two axes are different in direction from each other, and
wherein an angle between the two axes is 90° or approximately 90°.
2. The method for growing a group III nitride crystal according to claim 1 , wherein the melt-holding vessel is swung through an intermediary of a pressure vessel in which the melt-holding vessel is disposed.
3. The method for growing a group III nitride crystal according to claim 2 , further comprising:
feeding the nitrogen-containing gas at least one of (a) from a gas feeder disposed in a vicinity of the pressure vessel, and (b) from the gas feeder through an impurity remover disposed in a vicinity of the pressure vessel.
4. The method for growing a group III nitride crystal according to claim 1 , wherein the two axes are each a horizontal axis or a nearly horizontal axis.
5. The method for growing a group III nitride crystal according to claim 1 , wherein when a frequency of a swing motion about a first axis of the two axes is represented by fx and a frequency of a swing motion about a second axis of the two axes is represented by fy, relations 0.0033≦fx≦1 (Hz) and 0.0033≦fy≦1 (Hz) hold.
6. The method for growing a group III nitride crystal according to claim 5 , wherein swing frequencies about the first and second axes in a preliminary growth stage in which a temperature is increased to a predetermined temperature at which the melt is prepared are larger than swing frequencies about the first and second axes during crystal growth.
7. The method for growing a group III nitride crystal according to claim 5 , wherein a relation fx=fy holds.
8. The method for growing a group III nitride crystal according to claim 1 , wherein when a phase term of a swing motion about a first axis of the two axes is represented by Φx and a phase term of a swing motion about a second axis of the two axes is represented by Φy, a phase difference Φx−Φy is constant.
9. The method for growing a group III nitride crystal according to claim 8 , wherein a trajectory of an in-plane center of the melt-holding vessel is a Lissajous figure or approximately a Lissajous figure.
10. The method for growing a group III nitride crystal according to claim 1 , wherein a swing amplitude a about a first axis of the two axes and a swing amplitude b about a second axis of the two axes are equal to or approximately equal to each other.
11. The method for growing a group III nitride crystal according to claim 1 , wherein a swing waveform about each of the two axes is a sine wave or approximately a sine wave, or a triangle wave or approximately a triangle wave.
12. The method for growing a group III nitride crystal according to claim 1 , wherein a flow of the melt in a vicinity of a seed crystal in the melt-holding vessel is constant or approximately constant in magnitude and undergoes a periodic variation only with respect to a direction of the flow.
13. A method for growing a group III nitride crystal the method comprising:
growing a group III nitride crystal in a pressurized atmosphere of a nitrogen-containing as from a melt comprising at least a group III element, nitrogen and an alkali metal or an alkali earth metal; and
swinging a melt-holding vessel about two axes simultaneously, the melt-holding vessel holding the melt,
wherein the two axes are different in direction from each other, and
wherein at least one in-plane direction position of the melt-holding vessel is locally cooled.
14. The method for growing a group III nitride crystal according to claim 13 , wherein a position in the melt-holding vessel, corresponding to a central portion or a peripheral portion of a seed crystal is cooled.
15. The method for growing a group III nitride crystal according to claim 1 , wherein cooling is performed with a flow of the nitrogen-containing gas.