[16a-2J-1~12] 3.9 Terahertz technologies

▲ [16a-2J-4] [Young Scientist Presentation Award Speech] Low Temperature-Grown GaAs Carrier Lifetime Measurements Using "Double Optical Pump" Terahertz Time-Domain Emission Spectroscopy

〇Valynn Katrine Mag-usara¹, Stefan Funkner¹, Gudrun Niehues¹, Elizabeth Ann Prieto², Armando Somintac², Elmer Estacio², Arnel Salvador², Kohji Yamamoto¹, Muneaki Hase³, Masahiko Tani¹ (1.FIR-Univ. of Fukui, 2.Univ. of the Philippines, 3.Univ. of Tsukuba)

Keywords:charge carriers: generation and lifetime,terahertz wave,ultrafast spectroscopy

We propose and demonstrate "double optical pump" terahertz time-domain emission spectroscopy (THz-TDES) as an alternative technique to obtain information on the lifetime of photo-excited carriers in semiconductors. In a "double optical pump" THz-TDES scheme, a carrier injection pump pulse and a signal generation or reference pump pulse from the same femtosecond laser source are used to probe the decay characteristics of the THz generation in a semiconductor surface emitter. The surface electric field is screened by optical carriers generated by the carrier injection pump pulse. As such, the THz emission amplitude is expected to change with the relative time delay between the two optical pump pulses due to carrier decay. We implemented this technique for measurements of carrier lifetime in low temperature-grown gallium arsenide (LT-GaAs). The carrier lifetime values deduced from "double optical pump" THz emission decay curves show good agreement with data obtained from transient photo-reflectance measurements done on the same LT-GaAs samples grown by MBE at temperatures from 200°C-310°C.