Directional terahertz radiation from gainp lateral superlattice

We devised directionally controllable THz emission sources based on lateral composition modulation (LCM) structures. LCM structures were composed of In-rich Ga_{0 .-47} In_0-.53 P and Ga-rich Ga _{0 .-51} In_0.-49P layers whose period was in quantum scale of ∼15 nm. The inherent type II band alignment in these structures leads to electron-hole (e-h) separation and plays a key role in generating laterally polarized dipole ensembles, thus concomitantly emitting enhanced transmissive THz waves as compared to bulk sample. On the other hand, in lateral geometry, changes in THz fields between LCM and bulk structures turned out to negligible since the vertical electronic diffusion was allowed in both samples.