Optical Properties of GaInN/GaN Heterostructures and Quantum Wells

Photoreflection and photoluminescence spectroscopies have been used to identify details of the electronic bandstructure in GaInN/GaN strained heterostructures and multiple quantum well structures. Franz-Keldysh oscillations in the ternary layers are identified in both systems revealing large piezoelectric fields of 240 kV/cm (x=0.079, thin film) and 0.65 MV/cm (x=0.187). From spatially resolved luminescence a very narrow distribution ∆E =28 meV of the bandgap energy is derived (x=0.187). From the variation of the field with strain a piezoelectric coefficient dPz/dεzz=0.3 C/m is obtained corresponding to e14 = 0.1 C/m and an equilibrium polarization of GaN of Peq =43 mCm 2 is extrapolated in qualitative agreement with recent calculations.