Exclusion principle and screening of excitons in ${\mathrm{G}\mathrm{a}\mathrm{N}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ quantum wells

We model the variation of the exciton binding energy and of the oscillator strength versus temperature in strained ${\mathrm{G}\mathrm{a}\mathrm{N}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ quantum wells by using a self-consistent variational procedure. In addition, this method is extended to the case of high photoinjection conditions. We thus can properly account for the effect of a dense electron-hole plasma on the excitonic wave function, and we can quantitatively address the exciton bleaching phenomenon via quantum exclusion effects. A surprising behavior has been found: the robustness of the exciton to screening by the dense plasma increases with increasing temperature. In other words, the pumping intensity necessary to tear apart electrons and holes increases with increasing temperature. This is quantitatively interpreted in terms of the quantum exclusion effect as a straightforward result of the Pauli principle and of the fundamental prescriptions of quantum mechanics. The limitations imposed by this effect on the excitonic wave functions are relaxed with increasing temperature.