Interface-free GaAs structures—from bulk to the quantum limit

We have studied, through extensive transient PL (1.8 – 300 K) measurements, intrinsic recombination in “ideal” GaAs structures, passivated by state-of-the-art “surface barriers.” Lifetime versus GaAs thickness (10 µm − 0.01 µm) yields the lowest interface recombination velocities yet reported of ≤ 40 cm/s for MOCVD-prepared GaAs/Al_0.3Ga_0.7As double heterostructures and ~ 60 to 5500 cm/s for MOCVD-prepared all-GaAs n⁺/n⁻/n⁺ homostructures. In comparison, Na₂S passivation gives ~ 5500 cm/s, and bare GaAs surfaces yield ≥ 34,000 cm/s. Further, identical measurements made in comparably MBE-prepared GaAs/Al_0.3Ga_0.7AS double heterostructures suggest corresponding interface recombination velocities of ~ 250 to 5000 cm/s. Thus, we prove — from bulk to quantum wells — that “interface-free” GaAs structures are now achievable, and that intrinsic band-to-band and/or free exciton recombination may dominate in such structures.