Ultrafast Anisotropic Photocurrent in Indium Arsenide Photoexcited by Elliptically Polarized Light

Indium arsenide (InAs) with various excellent properties is an ideal material for Hall devices, magnetoresistance devices, terahertz source devices and so on. Due to its fascinating characters such as narrow bandgap, ultrahigh carrier mobility, high mobility ratio and so on, it affords an excellent platform for investigating ultraefficient terahertz radiation and the corresponding linear and nonlinear physical generation mechanisms. However, the transient photocurrents along three orthogonal orientations under circularly polarized excitation have not been systematically distinguished, which hinder the further improvement of the emission efficiency of terahertz source devices based on semiconductor InAs. Herein, we investigate the terahertz radiation mechanism of p-InAs (100) material using a reflection-type terahertz emission spectroscopy system. By analyzing the dependence of three orthogonal components of the terahertz signal emitted from InAs on the elliptically polarized state of the pump light, it is found that several physical mechanisms including strong photoinduced Dember effect, shift current, and tiny injection current concurrently contribute to terahertz emission in InAs. By combining nonlinear tensorial analysis, the contributions of different physical mechanisms along three orthogonal components to terahertz generation are qualitatively evaluated.