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

摘要

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 E_2 (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.