Luminescence of Zn- and Cd-doped GaN

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Abstract
The luminescence of epitaxial GaN layers doped with Zn or Cd during growth is characterized, at low doping levels, by the presence of an I1-type line at 3.455 eV at 4.2 K which is attributed to the decay of excitons bound to neutral [inverted lazy s] 190-meV deep Zn or Cd acceptors on Ga sites. In addition, a broad and very efficient (> 12% at 300 K) band centered around 2.85 eV is observed in both vapor- and solution-grown samples and completely dominates the spectrum at high doping levels. Contrary to the usual band-gap dependence, this ``blue'' emission band shifts to slightly higher energies with increasing temperature.