Blue-light emission from GaN self-assembled quantum dots due to giant piezoelectric effect

It is shown that the optical properties of GaN quantum dots with the wurtzite structure result from a balance between confinement and piezoelectric effects. In ``large'' quantum dots with an average height and diameter of 4.1 and 17 nm, respectively, the photoluminescence peak is centered at 2.95 eV, nearly 0.5 eV below the bulk GaN band gap. We attribute this enormous redshift to a giant 5.5 MV/cm piezoelectric field present in the dots, in agreement with theoretical calculations.