Spontaneous and piezoelectric polarization effects in wurtzite ZnO∕MgZnO quantum well lasers

Abstract

Spontaneous and piezoelectric polarization effects on electronic and optical properties of ZnO∕MgZnO quantum well (QW) structures are investigated by using the non-Markovian gain model with many-body effects. The spontaneous polarization constant for MgO determined from a comparison with the experiment is about −0.070C∕m2, which is larger than the value (−0.050C∕m2) for ZnO. The negligible internal field effect observed in the case of ZnO∕MgZnO QW structures with relatively low Mg composition (x<0.2) and thin well width (Lw<46Å) can be explained by the cancelation of the sum of piezoelectric and spontaneous polarizations between the well and the barrier. The ZnO∕MgZnO QW laser has much larger optical gain than the GaN∕AlGaN QW laser. This is attributed to the fact that the ZnO∕MgZnO QW structure has a larger optical matrix element due to the relatively small internal field, compared to the GaN∕AlGaN QW structure.