Piezoelectric Stark-like ladder in GaN/GaInN/GaN heterostructures

The electronic bandstructure of strained Ga1-xInxN wells between barriers of GaN is found to exhibit an unusual Stark ladder controlled mainly by the piezoelectric dipole across the strained layer. In luminescence and reflection spectroscopy four distinct steps including a strong redshift with respect to the thin film band gap are identified. Huge piezoelectric fields F less than or equal to 1 MV/cm are derived directly from Franz-Keldysh oscillations and interband transitions between carriers originating on opposite sides of the well. For the largest strain and electric field, a Stark-like ladder is identified. This provides important details for the interpretation of the electronic band structure in group-Ill nitride heterostructures.