Physical mechanisms of surface terahertz emission from semiconductors

Microscopic origin of THz emission from femtosecond laser excited narrow gap semiconductor surfaces is explained in terms of the photoelectron ballistic movement in non-parabolic and anisotropic conduction band. It has been shown that the azimuthal angle dependences of this emission are caused by the lateral photocurrent component resulting from that anisotropy. A strong THz radiation was observed from the lower symmetry crystal planes illuminated along their surface normal, which has allowed to demonstrate experimentally user-friendly line-of-sight THz emitters made from the bulk InAs and InSb, InAs pn diodes and p-i-n structures with GaInAs active layers.