Dependence of crystal quality on residual strain in strain-controlled thin AlN layer grown by metalorganic vapor phase epitaxy

Strain-controlled AlN layers were grown on (0001) 6H-SiC with a (GaN/AlN) buffer layer by metalorganic vapor phase epitaxy using an alternating-source-feeding technique (ASF). The successful strain and quality control of the thin AlN layer were experimentally demonstrated down to 0.05 mu m by changing the growth conditions of the (GaN/AlN) buffer layer. The quality of the AlN layer was evaluated by not only X-ray diffraction (theta-2 theta) but an X-ray rocking curve (omega-scan) from the viewpoint of c-axis tilting. The crystal quality was dependent on the residual strain in the AIN layer The (GaN/AlN)-buffer layer is effective in improving the quality of the AlN layer.