Giant piezoelectric effect in GaN self-assembled quantum dots

We observe in strained GaN self-assembled quantum dots grown on an AlN laye r, a dramatic modification of the optical emission spectra as the dot size varies. In "large" quantum dots with an average height of 4.1 nm, the photo luminescence (PL) peak is centered at 2.95 eV, nearly 0.5 eV below the bulk GaN bandgap. We attribute this enormous redshift to a giant 5.5 MV cm(-1) piezoelectric field present in our dots. Temperature-dependent PL studies r eveal the strongly zero-dimensional character of this QD system and are con sistent with an intrinsic PL mechanism. (C) 1999 Elsevier Science Ltd. All rights reserved.