Intraband relaxation time in wurtzite GaN/AlGaN quantum-well structures with spontaneous polarization effects

Spontaneous (SP) and piezoelectric (PZ) polarization effects on the intraband relaxation time for wurtzite (WZ) GaN/AlGaN quantum wells (QWs) are investigated theoretically as functions of structural parameters. These are also compared with the data for the flat-band (FB) model without an internal field. The linewidths for the carrier-carrier and carrier-phonon scatterings of the FB model are almost constant irrespective of the Al composition, while those of the self-consistent (SC) model decrease with the increase of the Al composition except for the h-ph scattering. Also, it is observed that the linewidths of the SC model are significantly reduced compared with those for the FB model, except for the h-ph scattering. The h-ph scattering for the SC model below ℏωLO has linewidths larger than the FB model due to the increase of the term related to the Fermi functions. The linewidths of both FB and SC models are almost constant irrespective of the well width, except for the e-h and h-e scatterings of the SC model. In the case of the e-h and h-e scatterings, the linewidths greatly decrease with the well width because of the increase of the spatial separation of wave functions. It is shown that the linewidths of both FB and SC models are a weak function of the barrier width.