Free and bound excitonic effects in Al(0.5)Ga(0.5)N/Al(0.35)Ga(0.65)N MQWs with different Si-doping levels in the well layers

Free exciton (FX) and bound exciton (BX) in Al(0.5)Ga(0.5)N/Al(0.35)Ga(0.65)N multiple quantum wells (MQWs) with different Si-doping levels in the well layers are investigated by photoluminescence (PL) spectra. Low temperature (10 K) PL spectra identify a large binding energy of 87.4 meV for the BX in undoped sample, and 63.6 meV for the BX in Si-doped (2 × 10(18 )cm(−3)) sample. They are attributed to O-bound and Si-bound excitons, respectively. The large binding energies of BX are assumed to originate from the strong quantum confinement in the quantum wells, which also leads to a stronger FX PL peak intensity in comparison with BX at 10 K. Si-doping is found to suppress the FX quenching by reducing threading dislocation density (TDD) in the well layers, leading to a significant improvement of IQE from 33.7% to 45%.