R. Cingolani et al., Spontaneous polarization and piezoelectric field in GaN/Al0.15Ga0.85N quantum wells: Impact on the optical spectra, PHYS REV B, 61(4), 2000, pp. 2711-2715
We have investigated the effects of the built-in electric field in GaN/Al0.
15Ga0.85N quantum wells by photoluminescence spectroscopy. The fundamental
electron heavy-hole transition redshifts well below the GaN bulk gap for we
ll widths larger than 3 nm for the specific quantum wells investigated and
exhibits a concomitant reduction of the intensity with increasing well thic
kness. The experimental data are quantitatively explained by means of a sel
f-consistent tight-binding model that includes screening (either dielectric
or by free-carriers), piezoelectric field and spontaneous polarization fie
ld. The impact of the built-in field on the exciton stability is discussed
in detail. We demonstrate that the exciton binding energy is substantially
reduced by the built-in field, well below the values expected from the quan
tum size effect in the flat band condition.