Built-in fields in non-polar InxGa1-xN quantum dots

We present a detailed analysis of the internal built-in potential in polar and non-polar In(1-x)Ga(x)N/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 e(15) 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 e(15) 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 e(15). However, this field is strongly reduced with increasing Ga concentration in the nanostructure. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim