Spontaneous polarization and piezoelectric effects on inter-subband scattering rate in Wurtzite GaN/AlGaN quantum-well

Spontaneous (SP) and piezoelectric (PZ) polarization effects on the inter-subband scattering rate for wurtzite (WZ) GaN/AlGaN quantum-well (QW) are investigated theoretically as functions of the sheet carrier density and the well thickness. This is also compared with the data obtained without the SP and PZ polarization effects. The SP polarization constant for AlN estimated from a comparison with the experimental results is about -0.060 C/m², which is lower than the value (-0.081 C/m²) calculated by theoretically. The SC model shows that scattering rates are largely reduced compared with those for the FB model. This is mainly due to the increase of the inverse screening length with inclusion of the PZ and SP polarization. The inverse screening length is obtained by assuming that electrons and holes exist in the well simultaneously. The intra-subband scattering rate at the subband edge increases with increasing carrier density and gradually decreases when the carrier density exceeds 10 × 10¹² cm^-2. On the other hand, the inter-subband scattering rate gradually decreases due to the increase of the inverse screening length with increasing carrier density.