Time-resolved photoluminescence as a probe of internal electric fields in GaN-(GaAl)N quantum wells

Very strong coefficients for spontaneous and piezoelectric polarizations ha ve recently been predicted for III-V nitride semiconductors with natural wu rtzite symmetry. Such polarizations influence significantly the mechanisms of radiative emissions in quantum-confinement heterostructures based on the se materials. The photoluminescence decay time of excitons is used as a pro be of internal electric fields in GaN-(Ga, Al)N quantum wells in various co nfigurations of strain, well widths, and barrier widths. The measured decay s are not only controlled by radiative lifetimes, which depend on the field s inside GaN wells but also on the nonradiative escape of carriers through Ga1 - xAlyN barriers, which depends on their widths and on the electric fie ld in these layers. It is shown in particular that the magnitude of the hel d in the wells is not a simple function of the strain of these layers via t he only piezoelectric effect, but rather the result of the interplay of spo ntaneous and piezoelectric polarizations in both well and barrier materials . [S0163-1829(99)02923-9].