Hot electron cooling in InSb probed by ultrafast time-resolved terahertz cyclotron resonance

Abstract

Measuring terahertz (THz) conductivity on an ultrafast time scale is an excellent way to observe charge-carrier dynamics in semiconductors as a function of time after photoexcitation. However, a conductivity measurement alone cannot separate the effects of charge-carrier recombination from effective mass changes as charges cool and experience different regions of the electronic band structure. Here we present a form of time-resolved magneto-THz spectroscopy which allows us to measure cyclotron effective mass on a picosecond time scale. We demonstrate this technique by observing electron cooling in the technologically-significant narrow-bandgap semiconductor indium antimonide (InSb). A significant reduction of electron effective mass from 0.032 me to 0.017 me is observed in the first 200 ps after injecting hot electrons. Measurement of electron effective mass in InSb as a function of photo-injected electron density agrees well with conduction band non-parabolicity predictions from ab initio calculations of the quasiparticle band structure.

The 2023 terahertz science and technology roadmap

“…For instance, characterization of birefringent materials where the birefringence originates from the mesoscopic structure provides exciting possibilities for industrial inspection [34]. Furthermore, THz polarimetry opens possibilities in the characterization of externally induced effects on materials: for example external magnetic fields allow the determination of Hall conductivity in a contactless fashion or the cyclotron effective mass of charge carriers on a picosecond timescale [35]. In addition, measurement of the full polarization state allows the determination of the complex optical properties of non-transmissive materials by ellipsometry [36].…”

Semiconductor Terahertz Physics

“…Terahertz cyclotron resonance has been employed to probe electron effective masses, [18] topologically protected states [19] and hot electron cooling. [20] Figure 2. Experimental reflectance spectroscopy of a layered HgCdTe sample and fit with a model involving Lorentz contributions from multiple layers.…”

“…Terahertz cyclotron resonance has been employed to probe electron effective masses, [ 18 ] topologically protected states [ 19 ] and hot electron cooling. [ 20 ]…”

Ultrawideband Solid-State Terahertz Phase Shifter Electrically Modulated by Tunable Conductive Interface in Total Internal Reflection Geometry

“…Terahertz (THz) technology has immense potential across a range of fields, including radar detection, − high-rate data communications, − real-time and high-resolution imaging, − material characterization, − and other fields. , However, due to the unique characteristics and constraints of terahertz waves, the vast majority of these applications are entirely dependent upon the fundamental THz devices, such as sources, detectors, and waveguides, as reviewed in 2017 and 2023 . Developing terahertz phase modulators, particularly those with wide bandwidths, remains a challenging task in this field.…”