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The deterioration of AlN quality caused by residual gallium in the MOCVD reaction chamber

After several repetitions of GaN epitaxial growth, the quality of the AlN template grown by metal–organic chemical vapor deposition deteriorated seriously, even when grown under the same procedure. However, the quality of the AlN template recovered a little the second time. It is found that this deterioration was enhanced if we increase the growth temperature. And this deterioration can be effectively weakened by omitting the baking procedure to cover the reactor chamber with AlN. The full width at half maximum of the X-ray rocking curve for AlN(102) significantly decreased from 1843 to 402 arcsec. This suggests that this deterioration of AlN quality is caused by residual gallium in the reactor chamber.