Initial growth behaviors of GaN layers overgrown by HVPE on one-dimensional nanostructures

The hydride vapor phase epitaxy of GaN on silicon covered by nanostructures

“…Comparing the above-discussed CL data of S1 and S2, we assume that the different morphology of the underlying nanostructure 1), where the density of the nanowalls of S1 is much higher than the density of NWs or nanoleaves of S2, resulting in a columnar growth with very different mean column diameters (0.3 μm for S1 and 2 μm for S2) during the low-T HVPE step. According to Kwon et al [14], the larger distance of the nanostructures serving as a template for HVPE overgrowth promotes lateral epitaxy and therefore results in larger grains during the first HVPE step. The very different mean column diameters formed during the low-T HVPE step resulted in different growth dynamics for S1 and S2 during the subsequent high-T HVPE step.…”

“…Hersee et al [9] proposed a nanoheteroepitaxy technique, taking advantage of three-dimensional stress relief mechanisms, which is expected to result in the further improvement of GaN epilayers grown on foreign substrates. Based on this method, several authors have discussed a new nonlithographic nanoheteroepitaxy approach, relying on self-assembled nanostructures in order to reduce the process steps and costs [10][11][12][13][14]. Kwon et al [14] have used a 50 nm thick sputtered AlN buffer on silicon, on which they have grown self-assembled nanoneedles and -rods during the first low-T HVPE step at 600 and 650 • C, respectively.…”

“…Based on this method, several authors have discussed a new nonlithographic nanoheteroepitaxy approach, relying on self-assembled nanostructures in order to reduce the process steps and costs [10][11][12][13][14]. Kwon et al [14] have used a 50 nm thick sputtered AlN buffer on silicon, on which they have grown self-assembled nanoneedles and -rods during the first low-T HVPE step at 600 and 650 • C, respectively. Subsequently, 0.5-2 μm thick GaN layers were overgrown in a second HVPE step at 1040 • C. The optical near-band-gap emission of these GaN layers is red-shifted with regard to the expected spectral position, the origin of which has not been analyzed in detail.…”