Influence of internal polarization fields on the disorder broadening of excitons in (In,Ga)N/GaN quantum wells

We investigate theoretically the impact of internal polarization fields on the disorder broadening of excitons in (In,Ga)N/GaN quantum wells consideri ng both uncorrelated alloy fluctuation and in-plane-correlated interface ro ughness in the frame of a center-of-mass separation approach. Not only the fluctuation of the band edges, but also the fluctuation of the long-range p olarization field of spontaneous and strain-induced dipole moments are take n into account. The polarization field is found to induce a narrowing of th e alloy contribution of the center-of-mass potential spectrum due to (i) pe netration of the carriers into the barriers and (ii) increased exciton volu me. Contributions from short-range interface roughness slightly weaken the narrowing, but do not reverse this effect. In case of a long-range interfac e roughness, a single-line decomposition of the spectrum occurs.