Direct evidence of photoluminescence broadening enhancement by local electric field fluctuations in polar InGaN/GaN quantum wells

In this work the effect of external electric field on the broadening of optical transitions in a triple polar InGaN/GaN quantum well is studied. Experimental investigation using photoluminescence and electroreflectance show that the reduction of the internal electric field by an external voltage reduces the broadening of the transitions. This is direct evidence that the broadening of photoluminescence in InGaN/GaN quantum wells is enhanced by the built-in electric field. This conclusion is supported by theoretical modelling within the random quantum well model. Additionally, we show that the exciton-phonon coupling can be controlled by an external electric field.