Effects of the spontaneous polarization and piezoelectric fields on the luminescence spectra of GaN/Al0.15Ga0.85N quantum wells

We have investigated the well width dependence of the ground level emission of GaN=AlGaN quantum wells. We nd that the fundamental electron{heavy-hole transition red-shifts well below the GaN bulk gap for well widths larger than 3 nm and that the luminescence intensity reduces with increasing well thickness. These eects originate from the quantum conned Stark eect caused by the strong built-in electric eld induced by the spontaneous polarization charge at the GaN=AlGaN interfaces and, to a minor extent, by the piezoelectric charge, with typical strength in the MV=cm range. The experimental data are quantitatively explained by means of a self-consistent tight-binding approach which includes screening (either dielectric or by free carriers) and spontaneous polarization eld.