Ultrafast conductivity dynamics in optically excited InGaN/GaN multiple quantum wells, observed by transient THz spectroscopy

We investigate ultrafast carrier dynamics in photoexcited InGaN/GaN multiple quantum wells by time-resolved terahertz spectroscopy. The initially very strong built-in piezoelectric field is screened upon photoexcitation by the polarized carriers, and is gradually restored as the carriers recombine. The conductivity related to the presence of photoexcited carriers, sensed by the THz probe pulses, shows a non-exponential, slowing-down decay with time, which is explained by the gradual restoration of the built-in field in the QWs and consequent quenching of recombination.

Screening and restoration of the built-in field are confirmed by the photoluminescence measurements.