Time evolution of piezoelectric field screening in InGaN quantum wells

We have experimentally observed the time evolution of the photoluminescence spectra of InGaN/GaN quantum wells with widths 3 and 4 nm in response to pulsed excitation at room temperature. We find that for both well widths the time evolution of the energy-integrated photoluminescence increases initially then decays and the spectrum displays a blue shift of the peak energy which then reverses. Through an iterative simulation of the carrier density, piezoelectric field and radiative recombination rate we calculate the behavior of these quantum well systems and find good agreement with the experimental data. The internal field present in the InGaN/GaN system is screened as carrier density increases, which combined with band filling and coulomb interactions result in a blue shift as the system is pumped and as recombination of the carriers occur a red shift is simulated. Although screening of the internal fields occurs our calculations show that at laser threshold there is still a large internal field present, 1.0 MVcm-1, which is 75 % of the unscreened value