Researchers at NIST have developed advanced non-contact methods to measure carrier dynamics in various semiconductor materials using ultrafast time-resolved terahertz (THz) spectroscopy. This technique allows them to monitor exciton formation, electron-hole separation, recombination, and free carrier dynamics in photo-excited nanofilms without physically contacting the samples.
The researchers used pulsed optical measurement techniques to study carrier generation, migration, and relaxation dynamics in bulk semiconductors, polymers, and mixed organic/organometallic photovoltaic nanofilms. Their findings could lead to the development of high-efficiency transparent conductors, 2D transistors, and solar cells.
The team also investigated bulk semiconductor mobility in commercial samples of silicon, GaAs, and other II-VI crystals using two-photon below bandgap excitation. They employed state-of-the-art, kHz repetition-rate amplified 45 femtosecond pulsed Ti: Sapphire lasers and optical parametric amplifiers to generate tunable sample excitation pulses and broadband THz probe pulses.
Collaborative studies with NIST and external groups focused on examining candidate 2D materials, semiconductors, perovskites, and high-efficiency donor-acceptor polymers and heterojunction mixtures, with a focus on optimizing photovoltaic applications using THz technology.
Keywords: THz, spectroscopy, carrier dynamics
