Pump dependent carrier lifetimes in InAs/GaAs quantum dot photoconductive terahertz antenna structures

Abstract

In this paper, we study the behavior of photoexcited carriers in GaAs wafers containing self-assembled InAs quantum dots (QDs). These samples were designed and grown to be employed as photoconductive antennae for terahertz (THz) generation. The implanted QDs serve to shorten the overall carrier lifetime and enable pumping with lasers operating at wavelengths between 1μm and 1.3μm. Optical pump-THz probe measurements reveal carrier lifetime shortening for higher pump powers in the unbiased antennae due to increased carrier capture via Auger relaxation. This phenomenon significantly broadens the THz spectra from QD-based PCAs and explains the increased THz intensity at higher frequencies presented earlier.