We demonstrate a method for reliably determining the electrical properties of graphene including the carrier scattering time and carrier drift mobility from terahertz time- domain spectroscopy measurements (THz-TDS). By comparing transients originating from directly transmitted pulses and the echoes from internal reflections in a substrate, we are able to extract electrical properties irrespective of random time delays between pulses emitted in a THz-TDS setup. If such time delays are not accounted for they can significantly influence the extracted properties of the material. The technique is useful for a robust determination of electrical properties from THz-TDS measurements and is compatible with substrate materials where transients from internal reflections are well-separated in time.Innovation Fund Denmark (0603-005668B); Danish National Research Foundation (DNRF103); EU Horizon 2020 (696656); Danish Council for Independent Research (64092); EPSRC Doctoral Training Award (EP/M506485/1)
