TO₁ soft mode in Fe doped β-Ga₂O₃ studied by terahertz time domain spectroscopy

Abstract The transmission spectra of terahertz (THz) waves through Fe doped β-Ga2O3 in the range of 1-6 THz by air-plasma-based THz time-domain spectroscopy (THz-TDS) at room temperature and their temperature dependence between 90 and 500 K in the range of 0.7 THz-1.8 THz have been measured. We estimated the complex dielectric constants by fitting the spectra with the classical damped oscillator dispersion model and obtained the anisotropic lowest transverse optical (TO1) phonon frequencies. The values at room temperature agreed with the reported values, and no significant temperature dependence was observed.