Step-flow growth of GaN(0001) on 4H-SiC(0001) by plasma-assisted molecular beam epitaxy

Journal article, 2016

We report on step-flow growth of GaN(0001) on 4H-SiC(0001) substrates by plasma-assisted molecular beam epitaxy. The GaN layers were deposited directly on the substrate without using a buffer layer. A growth temperature of 900 degrees C and above resulted in an atomically flat surface morphology with locally straight steps indicating step-flow growth. The step height was 0.21 nm corresponding to one-half unit cell. The terrace width was 97 nm and the root-mean-square roughness was 0.06 nm. Samples grown below 900 degrees C exhibited a surface morphology consisting of spiraling terraces forming hexagonal hillocks. The full-width at half-maximum for X-ray rocking-curves recorded across the (0002) and (10 (1) over bar5) reflections was as narrow as 62 and 587 arcsec, respectively. We show that the high growth temperature in conjunction with Ga adlayers on the growth front provides a path for achieving step-flow growth of GaN by MBE.