Screened excitons in strained wurtzite AlxGa1-xN/GaN/AlyGa1-yN quantum wells

The binding energies of heavy-hole excitons in asymmetric strained wurtzite AlxGa1-xN/GaN/AlyGa1-yN quantum wells are investigated theoretically with a variational method and a self-consistent procedure. The screening effect due to the 2-dimensional electron-hole gas and the built-in electric field produced by spontaneous and strain-induced piezoelectric polarization are considered in our calculation. The result indicates that the strong built-in electric field is modulated obviously by the well width, barrier thickness and Al content. The decrease of well width increases the absolute value of built-in electric field in the well layer, but reduces the strength of the field in barrier layers. The calculated results are found in agreement with previous works in symmetric structures but the strong built-in electric field modulated by the barrier thickness and Al content results in the reduction of the excitonic binding energy in asymmetric ones. It is also found that the screening effect on the coloumbic interaction of electron and hole is stronger than on the built-in electric field, leading to a reduction of excitonic stability. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim