Selective observation of transverse optical phonons of Au modes to evaluate free charge carrier parameters in β-Ga2O3 substrate and homoepitaxial film

Polarized infrared reflectance spectra from beta-Ga2O3 (001) unintentionally doped (undoped) and Sn-doped substrates were investigated. Spectra from an undoped homoepitaxial film grown on the Sn-doped substrate were also investigated. By setting the electric field vector of the incident light E parallel to the crystallographic b-axis in the s-polarized configuration, the spectra for pure transverse optical phonons of A(u) modes were well reproduced by the Drude-Lorentz model. Subsequently, the free-carrier concentrations and carrier mobilities were determined to be in reasonable agreement with those determined by Hall-effect measurements, and at the same time, the film thickness was determined for the homoepitaxial layer. The results ensure the validity of the simplified optical model analyses for any arbitrary surface orientations where the b-axis is parallel to the surface only if no birefringence effects are present by choosing as E//b in s-polarized configuration.

Automated summary

The study investigated polarized infrared reflectance spectra from beta-Ga2O3 (001) unintentionally doped and Sn-doped substrates using the Drude-Lorentz model. The results successfully reproduced the spectra of pure transverse optical phonons and determined the free-carrier concentrations and carrier mobilities in agreement with Hall-effect measurements. Additionally, the study determined the film thickness for the homoepitaxial layer, ensuring the validity of the simplified optical model analyses for arbitrary surface orientations.