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

Abstract

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.