Seeded Growth of AlN Layers on Al- and N-Polar AlN Seeds by the Cu-Al-Ca Solution Growth Method

Herein, the growth behavior of aluminum nitride (AlN) layers on the Al-polar and N-polar surfaces of AlN seeds is investigated by the Cu-Al-Ca solution growth method. AlN layers with a thickness of 50-60 mu m grow on N-polar seeds in 5 h, whereas the thickness of the AlN layer on the Al-polar seeds reaches approximately 35-50 mu m. Optical microscopy, X-ray diffraction, high-resolution X-ray diffraction (HRXRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy are performed to investigate the morphology and crystal quality of the grown AlN layers. The N-polar and Al-polar surfaces show hillock growth, which is consistent with the hexagonal structure of AlN. However, the surfaces show differences in terms of hillock size (smaller on the N-polar surface). The HRXRD rocking curves of (002) and (102) show full-width at half-maximum (FWHM) values of 160.25 and 33.53 arcsec, respectively. From Raman analysis, the FWHM values of the AlN layers on the N-polar and Al-polar seeds are 6.1 and 10.6 cm(-1), respectively. The PL results show 310, 460, and 590 nm emission peaks of the AlN layer, which may be caused by oxygen impurity and V-N (nitrogen vacancy) and Al-i (aluminum gap).