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

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