The recombination velocity at oxide–GaAs interfaces fabricated byinsitumultiple‐chamber molecular beam epitaxy has been investigated. Ga2O3, Al2O3, SiO2, and MgO films have been deposited on clean, atomically orderedn‐ andp‐type (100) GaAs surfaces using molecular beams of Ga–, Al–, Si–, and Mg oxide, respectively. Based on the internal quantum efficiency measured for incident light power densities 1≤P0≤104W/cm2, the interface recombination velocityShas been inferred using a self‐consistent numerical heterostructure device model. While Al2O3–, SiO2–, and MgO–GaAs structures are characterized by an interface recombination velocity which is comparable to that of a bare GaAs surface (&bartil; 107cm/s),Sobserved at Ga2O3–GaAs interfaces is as low as 4000–5000 cm/s. The excellent Ga2O3–GaAs interface recombination velocity is consistent with the previously reported low interface state density in the mid 1010cm−2 eV−1range. ©1996 American Institute of Physics.