Dynamics of free carriers – neutral impurity related optical transitions in Be and Si δ-doped GaAs/AlAs multiple quantum wells: Fractional-dimensional space approach

The dynamics of impurity-related optical transitions in 20 nm wide silicon and beryllium δ-doped GaAs/AlAs multiple quantum wells with various doping levels has been investigated at near liquid helium temperatures. The radiative lifetimes of the free electron-neutral acceptor and the free hole-neutral donor have been identified. The capture cross-sections of the free electrons by neutral Be acceptors were experimentally determined to σ e-Be  = 4 × 10 –10  cm, whereas this corresponded to σ h-Si  = 2.2 × 10 –8  cm for the free holes by neutral Si donors. The experimentally determined cross-section ratio of σ h-Si /σ e-Be  = 55 is close to the estimated 2D value of σ h-D /σ e-A  = 64 and remains lower compared to the calculated value for the 3D case of σ h-D /σ e-A  = 121.