Strong optical polarization in nonpolar(1{1¯}00)AlxGa{1-x}N/AlN quantum wells

Abstract

The optical polarization properties in nonpolar (1{1¯}00) AlxGa{1−x}N/AlN quantum wells (QWs) are investigated over the full range of Al compositions. The k⋅p calculation predicts that the lowest energy optical transition in (1{1¯}00) AlxGa1−xN layers pseudomorphically grown on unstrained AlN is dipole allowed for the electric field vector parallel to the [0001] direction, and that the degree of polarization is hardly affected by the AlxGa{1−x}N QW width regardless of the Al composition. Experimentally, AlxGa{1−x}N/AlN QWs (0≤x≤0.81) are homoepitaxially grown on AlN substrates. Photoluminescence spectroscopy reveals that the emissions of all QWs, including GaN/AlN QWs, are strongly polarized along the [0001] direction. This result agrees with the theoretical prediction.