Pulse Source Injection Molecular Beam Epitaxy and Characterization of Nano-scale Thin GaN Layers on Si Substrates

We report the successful growth of thin GaN layers on (I11) orientated Si substrates utilizing a newly developed pulse source injection molecular beam epitaxial (PSIMBE) technique. RHEED patterns showed that two-dimensional layer-by-layer growth started at a very early stage during deposition (within 20 nm). AFM studies showed that an almost atomically smooth surface was obtained with an area RMS roughness of less than 0.2 nm. The crystal structure and quality were determined from high resolution 2-Theta-Omega scan and exhibited only three strong and sharp lines at 28.56, 34.70 and 73.05 degrees due to the Si substrate and the single crystalline wurtzite (w-) GaN (0002) and (0004), respectively. Raman scattering study showed the characteristic w-GaN E2 band at 565 wave-numbers and the longitudinal optical (LO) phonon-plasma coupling mode at 731 cm-1. These data indicate the success of the DIBE growth of single crystalline w-GaN thin layers on the order of less than 100-nm thick on Si substrates without using a complicated buffer structure.