Steady state and time-resolved differential transmission spectroscopy in a strained ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}/\mathrm{G}\mathrm{a}\mathrm{N}$ multiple quantum well structure embedded within a p-i-n structure has been studied to identify the dominant screening mechanisms and measure the carrier sweep-out time. The results are consistent with a long-range out-of-well carrier screening where the photoexcited carriers escape the wells and separate, creating a space-charge field that induces an increase of the in-well field and shifts the excitonic transition to lower energies. A redshift of excitonic resonance under photoexcitation suggests that the direction of in-well field is opposite to that in the barriers due to the piezoelectric polarization in this strained ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ well. Compared with GaAs multiple quantum wells, a long carrier sweep-out time of 650 ps was observed in this structure.

• Received 10 June 2003

DOI:https://doi.org/10.1103/PhysRevB.68.233304