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 ΔE=28 meV of the bandgap energy is derived (x=0.187). From the variation of the field with strain a piezoelectric coefficient dP_z/dε_zz=0.3 C/m ² is obtained corresponding to e₁₄=0.1 C/m² and an equilibrium polarization of GaN of P_eq=43 mCm ² is extrapolated in qualitative agreement with recent calculations