Spontaneous polarization and piezoelectric effects on intraband relaxationtime in a wurtzite GaN/AlGaN quantum well

Spontaneous (SP) and piezoelectric (PZ) polarization effects on the intraba nd relaxation time for a wurtzite (WZ) GaN/AlGaN quantum well (QW) are inve stigated theoretically as functions of the sheet carrier density and well t hickness. The self-consistent (SC) model with the SP and PZ polarizations s hows that linewidths for carrier-carrier and carrier-phonon scatterings are significantly reduced compared to those for the flat-band (FB) model witho ut SP and PZ polarization. In particular, line-widths fur the e-h and h-e s catterings are reduced by about two orders of magnitude at a sheet carrier density as low as 2 x 10(12) cm(-2) compared to the case of the FB model, T his is attributed to the decrease of the matrix element due to the spatial separation between electron and hole wave functions. In the case of the e-e and h-h scatterings, the reduction of linewidths is mainly attributed to t he decrease of the scattering matrix element due to the increase of the inv erse screening length. Linewidths for e-h and h-e scatterings gradually inc rease with the sheet carrier density since the screening held increases, wh ile linewidths for the other scatterings are almost independent of the shee t carrier density. The SC model also shows that linewidths for the carrier- carrier and carrier-phonon scatterings are nearly, constant irrespective of well thickness except for e-h and h-e scatterings. In the case of e-h and h-e scatterings, linewidths greatly decrease with the well width because of the increase of the spatial separation of wave functions.