Stress study of GaN grown on serpentine-channels masked Si(111) substrate by MOCVD

An advanced epitaxial lateral overgrowth (ELOG) structure named “serpentine-channels masked Si(111) substrate” has been introduced, which only has one high-defect region per period compared with the conventional ELOG method. We successfully obtained both coalesced and uncoalesced GaN layers on the substrate simultaneously by the metal-organic chemical vapor deposition (MOCVD) method. The stress states of these two kinds of GaN epilayers were investigated by room-temperature micro-Raman scattering technique. The stress level in the uncoalesced GaN layer was a little lower than that in the coalesced GaN layer. Raman spectra reveal the periodical variations of residual tensile stress in GaN by analyzing E2 (high) phonon mode. In addition, thermal stress distribution of GaN was simulated by elasticity theory using the finite-element method (FEM). The results of simulation are entirely consistent with the experimental results derived from micro-Raman measurements.