Built-in electric field in ZnO based semipolar quantum wells grown on (101¯2) ZnO substrates

We report on the properties of semipolar (Zn,Mg)O/ZnO quantum wells homoepitaxially grown by molecular beam epitaxy on (101¯2) R-plane ZnO substrates. We demonstrate that atomically flat interfaces can be achieved with fully relaxed quantum wells because the mismatch between (Zn,Mg)O and ZnO is minimal for this growth orientation. The photoluminescence properties evidence a quantum confined Stark effect with an internal electric field estimated to 430 kV/cm for a 17% Mg content in the barriers. The quantum well emission is strongly polarized along the [1¯21¯0] direction and a comparison with the semipolar bulk ZnO luminescence polarization points to the effect of the confinement.