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/Al0.3Ga0.7As double heterostructures and - 60 to 5500 cm/s for MOCVD-prepared all-GaAs n+/n-/n+ homostructures. In comparison, Na2S passivation gives approximately 5500 cm/s, and bare GaAs surfaces yield ≥ 34.000 cm/s. Further, identical measurements made in comparably MBE-prepared GaAs/Al0.3Ga0.7As double heterostructures suggest corresponding interface recombination velocities of approximately 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.