Spontaneous emission spectra of GaAsBi/GaAs double quantum well structures

This study systematically investigates the spontaneous emission spectra of GaAs_1-xBi_x/GaAs double quantum wells (DQWs) through an eight-band k•p model, elucidating the dependence of the emission characteristics across varying well widths, barrier thicknesses, Bi compositions, doping densities, and temperatures. The emission peak intensity decreases and redshifts with increasing well-width due to weakened quantum confinement, with DQWs showing a more gradual intensity decay than SQWs. The GaAs barrier thickness of the DQWs is found to affect minimally the spontaneous emission spectra, but a GaAs_0.95Bi_0.05/GaAs DQW, where the interwell barrier is a GaAs_0.99Bi_0.01 barrier layer, demonstrates the tunability of the emission intensity with varying barrier thickness. Varying the Bi composition in the GaAs_1-xBi_x wells of the DQWs shows invariant peak intensity across low compositions (0.01–0.05) and a pronounced redshift over 30 meV. On the other hand, simultaneous variation of Bi compositions in both wells enables a monotonic redshift. This shows a method to realize a broadband frequency tunability. A thicker interwell GaAs_1-xBi_x barrier layer, for a specified Bi composition, can result in a relatively larger redshift. Increased carrier density boosts peak intensity. As the temperature increases, the peak intensity decreases, and the peak position undergoes a redshift. Notably, DQWs exhibit slower decay rates at high energies compared to SQWs. Furthermore, under equivalent confinement conditions, DQWs demonstrate superior emission rates relative to SQWs.