Nonlinear behavior of photoabsorption in hexagonal nitride quantum wells due to free carrier screening of the internal fields

We investigate the effects of large electron-hole pair densities on the energy spectra of quantum wells based on hexagonal group-III nitrides, such as ${\mathrm{G}\mathrm{a}\mathrm{N}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ or ${\mathrm{In}}_y{\mathrm{Ga}}_{1-y}\mathrm{N}/\mathrm{G}\mathrm{a}\mathrm{N}$ systems. More specifically, we solve self-consistently the Schrödinger and Poisson equations in order to calculate the changes in emission and absorption spectra, induced by the screening of the large internal electric fields that are present in these systems. In particular, we find that pair densities of a few times ${10}^{12}{\mathrm{cm}}^{-2}$ induce not only a blueshift of the fundamental transition but also a significant enhancement of the absorption coefficient, in the region corresponding to transitions between excited states. We estimate the typical optical power densities necessary to induce such effects.