THz spectroscopy of the ammonothermal p-type GaN substrate with and without AlGaN/GaN epilayers

Complex refractive index of the ammonothermal p-type GaN substrate and on top grown AlGaN/GaN epilayers were measured by the terahertz time domain spectroscopy over the frequency range 0.1 to 3.0 THz. High THz transparency and low dispersion of the refractive index were observed for different conductivity p-type GaN semiconductor samples.