Micro-Raman Investigation of Epitaxial Lateral Overgrown Cubic GaN on Patterned GaAs (001) with Different Mask Stripe Directions

Abstract

Epitaxial lateral overgrowth (ELO) was performed to grow cubic GaN layers on stripe-patterned GaAs (001) substrates via metalorganic vapor phase epitaxy. Growth time was varied from 10 to 120 minutes to investigate an evolution of growth morphologies and crystal structures of GaN, which were respectively analyzed by scanning electron microscopy and micro-Raman scattering spectroscopy. Growth features of ELO cubic GaN for [1-10] oriented mask stripe-pattern showed the {113} side-wall facets. On the other hand, the {111} side-wall facets were observed for ELO cubic GaN grown on the [110] oriented mask stripe-pattern. In case of [100] oriented mask stripe-pattern, growth feature with top rough surface and unclear side-wall facets was obtained. Micro-Raman spectroscopy was used as a tool to identify both cubic and hexagonal GaN structures performed on surface of the top and side-wall facets of the GaN stripes. ELO cubic GaN layer with growth time of 60 min along the [1-10] oriented mask stripe-pattern exhibited the highest ratio of cubic to hexagonal GaN, which was examined from an integrated intensity of LO phonon mode at 738 cm-1 for cubic GaN comparing with that of hexagonal GaN, appearing at A1 (TO) 538 cm-1, E1 (TO) 558 cm-1 and E2 (high) 568 cm-1.