Optical Study of Bandedge Blue-Shift in AlGaN/GaN Double Quantum Wells

Optical properties of AlGaN/GaN double quantum wells grown by metalorganic chemical vapor deposition are investigated. The wide-angle and small angle x-ray diffraction spectra show high crystalline quality of the sample. Optical transmission and cathodoluminescence spectra exhibit that there is a blue shift of the energy bandedge in the AlGaN/GaN double quantum wells comparing to that of bulk GaN. The experimental data are compared to theoretical calculation based on the finite square well model and a confined particle transitions are identified. The observed energy shift which differs from calculated values of ground state electron to heavy hole transition is attributed to strain in the AlGaN/GaN system.