Free-carrier electrorefraction and electroabsorption in wurtzite GaN.

Abstract

We present a theoretical analysis of the change in refractive index and absorption of Wurtzite GaN due to free carriers for a wavelength range of 1 to 5 μm using the Drude model. The separate role of holes and electrons as well as their combined effect are discussed and the results are compared to those of Si and GaAs. The results show that promising modulators based on electrorefraction and electroabsorption can be implemented in a GaN integrated photonic platform. We also discuss the validity of the Drude model as well as the interaction of longitudinal optical (LO) phonons in GaN with the electron-hole plasmons, especially the impact on the absorption of GaN at high carrier concentrations. While LO phonon-plasmon (LOPP) interaction is shown to be stronger for electrons than for holes, the overall effect is negligible at the wavelength range of discussion (1-5 µm) for the moderate injection levels examined here for carrier-induced electro-optic modulation.