| 摘要 |
PROBLEM TO BE SOLVED: To relax the strain due to the difference between the thermal expansion coefficients of a sapphire substrate and a gallium nitride crystal by a method wherein a buffer layer of a specified structural formula is used on the sapphire substrate. SOLUTION: The growth of a gallium nitride(GaN) crystal is performed using an organic metal vapor growth (MOVPE) method. Before the growth, a sapphire substrate (Al2 O3 substrate) 60 is subjected to organic cleaning by ultrasonic waves and thereafter, the substrate 60 is installed in a reaction furnace of an MOVPE unit. After the interior of the furnace is evacuated, the substrate 60 is heated for about 15 minutes at about 1100 deg.C in a hydrogen atmosphere of about 70Torr and the surface of the substrate is subjected to cleaning. In the case where the GaN crystal is grown on the substrate 60, first, the substrate 60 is cooled down to about 500 deg.C and thereafter, about 2μmol/ minute of a trimethylgallium(TMG), 2.5L/minute of ammonia and a 2L/minute of carrier hydrogen are fed to the substrate to grow a low-temperature GaN buffer layer 61 in a thickness of about 30nm on the substrate 60. Then, after a GaN buffer layer 62 is grown in a thickness of the about 500nm at about 1000 deg.C, 10μmol/minute of a TMA is flowed to grow an Alx Ga1-x N (0.10<=x<=0.14) layer 63 in a thickness of about 2μm at about 1000 deg.C. |
