Terahertz emission fromGa1−xInxSb

Abstract

We report an experimental study on terahertz (THz) emission from ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{In}}_{x}\mathrm{Sb}$ with $0\ensuremath{\le}x\ensuremath{\le}1$. THz emission is excited by femtosecond near-infrared laser pulses. For this material system THz emission is maximized for an In mole fraction $x\ensuremath{\approx}0.5$. The maximum in THz emission occurs as a result of carrier compensation $({N}_{A}\ensuremath{\approx}{N}_{B})$ for this specific material composition. The THz emission from $n$-type $\mathrm{InSb}$ is twice as large than that from $p$-type $\mathrm{GaSb}$. The THz emission from ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{In}}_{x}\mathrm{Sb}$ is explained according to the photo-Dember model. The ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{In}}_{x}\mathrm{Sb}$ material system enabled the study of the influence of carrier concentrations on the THz emission process in narrow band gap semiconductors. Our study demonstrates the existence of a compromise between the positive effect of high electron temperature provided by narrow band gap materials and the negative effect of a high intrinsic carrier concentration. This compromise dictates the extent to which the band gap in a semiconductor can be reduced in order to enhance the THz emission. This same analysis can be extended to explain why the THz emission from $\mathrm{InSb}$ is lower than that of $\mathrm{InAs}$.