Terahertz emission from Ga1-xInxSb

We report an experimental study on terahertz (THz) emission from Ga1-xInxSb with 0 <= x <= 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 approximate to 0.5. The maximum in THz emission occurs as a result of carrier compensation (N-A approximate to N-B) for this specific material composition. The THz emission from n-type InSb is twice as large than that from p-type GaSb. The THz emission from Ga1-xInxSb is explained according to the photo-Dember model. The Ga1-xInxSb 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 InSb is lower than that of InAs.