We use a surface-integral method to determine the polarization potential in nitride-based quantum dots (QDs) grown on a nonpolar substrate. There is uncertainty in the literature regarding the sign of the piezoelectric constant $e_{15}$. We find that only a negative $e_{15}$ can give the reduced electrostatic built-in field found experimentally in nonpolar GaN/AlN QDs. Our analysis of nonpolar InN/GaN QDs indicates that a significant built-in field remains in these structures. We calculate that despite the reduced polarization potential, ground-state electrons and holes can remain spatially separated in GaN/AlN QDs.

• Received 2 December 2008

DOI:https://doi.org/10.1103/PhysRevB.79.081401