Impact ionization in InSb probed by terahertz pump—terahertz probe spectroscopy

Abstract

Picosecond carrier dynamics in indium antimonide (InSb) following excitation by below band gap broadband far-infrared radiation was investigated at 200 and 80 K. Using a THz-pump/THz-probe scheme with pump THz fields of 100 kV/cm and an intensity of $100\text{ }\text{MW}/{\text{cm}}^{2}$, we observed carrier heating and impact ionization dynamics. The number of carriers produced exceeds ${10}^{16}\text{ }{\text{cm}}^{\ensuremath{-}3}$, corresponding to a change in carrier density $\ensuremath{\Delta}N/N$ of 700% at 80 K. The onset of a well-defined absorption peak at 1.2 THz is an indication of changes in longitudinal optical (LO) and longitudinal acoustic (LA) phonon populations due to cooling of the hot electrons.