Strikingly Different Behaviors of Photoluminescence and Terahertz Generation in InGaN/GaN Quantum Wells

We have investigated photoluminescence (PL) and terahertz (THz) generation simultaneously from multiple InGaN/GaN quantum wells (QWs) with different well periods. The PL intensity fully saturates when the period of QWs is increased up to 4. However, THz output power continuously scales up even if the period of QWs is increased up to 16. Such a behavior indicates that high-power THz wave can be generated without efficient recombination of the photogenerated carriers, since THz is only generated during the absorption process. Following the measurements of intensity and peak energy of PL together with output power and spectra of THz, we have concluded that the screening effect induced by photo-generated carriers can be neglected when the pump fluence is as low as 85 μJ/cm
²
.