Theory of GaN Quantum Dots for Optical Applications

The optical properties of III-N wurtzite heterostructures are dominated by the built-in polarization potential. We first review the dependence of III-N bulk valence band structure on strain and the key factors determining the polarization vector in polar and nonpolar quantum wells, including electromechanical effects. We then present a surface integral technique to determine the built-in potential in quantum dots (QDs) of arbitrary shape. We show for polar QDs how the polarization potential spatially separates electrons and holes vertically but confines them laterally, causing the radiative recombination rate to decrease rapidly with increasing dot height and a strong blueshift with increasing carrier density. Finally, we show that although the polarization potential can be much reduced in nonpolar GaN/AlN QDs, it is likely to remain significant in nonpolar InN/GaN QD structures.