Growth evolution and pendeo-epitaxy of non-polar AlN and GaN thin films on 4H–SiC (1 1 2¯ 0)

The initial and subsequent stages of growth of AlN on 4H–SiC (1 1 2¯ 0) and GaN on AlN (1 1 2¯ 0) have been investigated using atomic force microscopy and X-ray photoelectron spectroscopy. The AlN nucleated and grew via the Stranski–Krastanov mode. Densely packed, [0 0 0 1]-oriented individual islands were observed at 10 nm. Additional deposition resulted in the gradual reorientation of the growth microstructure along the [1 1¯ 0 0]. GaN formed via the Volmer–Weber mode with rapid growth of islands along the [1 1¯ 0 0] to near surface coverage at a thickness of 2 nm. Continued deposition resulted in both faster vertical growth along [1 1 2¯ 0] relative to the lateral growth along [0 0 0 1] and a [1 1¯ 0 0]-oriented microstructure containing rows of GaN. Fully dense GaN films developed between 100 and 250 nm of growth, and the preferred in-plane orientation changed to [0 0 0 1]. Lateral growth of GaN films reduced the dislocation density from ∼4×1010 to ∼2×108 cm−2. The high concentration of stacking faults (∼106 cm−1) was also reduced two orders of magnitude.