Built-in fields in non-polar In_xGa_1-xN quantum dots

We present a detailed analysis of the internal built-in potential in polar and non-polar In_1-xGa_xN/GaN quantum dots (QDs). The applied model is based on a surface integral method to calculate the three-dimensional electrostatic built-in potential in semiconductor QDs of arbitrary shape. This technique allows for a detailed and systematic analysis of the different contributions to the total built-in field. Here, we also investigate the impact of the QD geometry on the built-in potential in structures grown along non-polar directions of the crystal. Since there is uncertainty in the literature as to the sign of the piezoelectric constant e₁₅ associated with the shear strain, we study the influence of this constant in detail. While recent results on non-polar GaN/AlN QDs indicate that only a negative e₁₅ leads to significant reduction in the built-in field, we show that for InN/GaN QDs there should still be a significant field present, independent of the sign of the piezoelectric constant e15. However, this field is strongly reduced with increasing Ga concentration in the nanostructure.