Comparison of transport, recombination, and interfacial quality in molecular beam epitaxy and organometallic vapor-phase epitaxy GaAs/Al _xGa_1-xAs structures

We have studied free-carrier recombination and transport in GaAs structures prepared by different epitaxial growth techniques and with different "surface barriers" including molecular beam epitaxy (MBE) and organometallic vapor-phase epitaxy (OMVPE) prepared undoped, symmetric GaAs/Al0.3Ga 0.7As double heterostructures and these same structures after etch removing the top Al0.3Ga0.7As layer and repassivating with Na2S. We find 300-K lifetimes of ≥2.5 μs (350 ns), and interface recombination velocities of 40 cm/s (250 cm/s) for our OMVPE (MBE) structures. Identical measurements for Na2S and bare surfaces yield interface recombination velocities of 5500 cm/s and 34 000 cm/s, respectively. Free-carrier transport in both types of structures is diffusive with hole mobilities of ∼350 cm2/V s.