Mesoscopic-capacitor effect in ${\mathrm{G}\mathrm{a}\mathrm{N}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ quantum wells: Effects on the electronic states

We show that wide GaN quantum wells behave like mesoscopic capacitors. The electron-hole pairs are separated by the spontaneous and piezoelectric polarization fields and accumulated in the well, resulting in a well-width dependent screening of the built-in field. The extent to which such screening is effective depends on the interplay between radiative and nonradiative recombination probabilities, which deplete the ground level of the quantum well, causing the recovery of the unscreened built-in field. The account of the mesoscopic capacitor effect provides a quantitative description of the optical spectra and of the time dynamics of a set of high quality quantum wells with well characterized structural parameters.