Based on all-electron density-functional theory calculations using the generalized gradient approximation, we demonstrate the continuous tunability of the band gap and strength of the built-in electric field in GaN/AlN (0001) superlattices by control of the thickness of both the well (GaN) and barrier (AlN) regions. The effects of strain for these quantities are also studied. Calculations taking into account the self-interaction correction exhibit the same dependence on thickness. The calculated electric field strength values are in good agreement with recent experiments. Spontaneous polarization dominates the contribution to the electric field and the strain-induced piezoelectric polarization is estimated to contribute only about 5–10%.

• Received 24 September 2009

DOI:https://doi.org/10.1103/PhysRevB.81.155301