Effect of Si doping on epitaxial lateral overgrowth of GaN: A spatially resolved micro-Raman scattering study

We report spatially resolved Raman scattering from Si-doped epitaxial laterally overgrown GaN structures to investigate spatial variations in stress and free electron concentration. The doping-induced increase in the free electron concentration is relatively higher in the laterally overgrown regions than in the coherently grown regions due to the increased contribution of the high-energy A ₁ longitudinal optical phonon-plasmon coupled mode. In addition, the E ₂(high) [E ₂(low)] phonon energy shifts downward (upward) more significantly in the laterally overgrown regions than in the coherently grown regions. The doping-induced Raman shifts of the E ₂(high) and E ₂(low) phonons in the laterally overgrown regions are approximately -0.6 and 0.11 cm ^-1, respectively, corresponding to the in-plane stress of ∼0.22 GPa.