We demonstrate an in situ mask removal technique for use in selective area epitaxy (SAE) by metal organic chemical vapor deposition (MOCVD). The mask material is native aluminum oxide (AlxOy) formed by wet thermal oxidation of a thin AlGaAs layer. The AlxOy layer is patterned using standard photolithography and wet chemistry outside of chamber. The AlxOy layer forms a high-quality, pin-hole- free SAE mask that can be removed within the MOCVD chamber using an in situ HCl etch process. After in situ mask removal, subsequent growth processes produce an atomically smooth and uniform surface. Scanning electron microscopy and atomic force microscopy are used to characterize surface features and measure RMS roughness after each processing step. Using this processing scheme, we form a buried InGaAs quantum well stripe that emits room-temperature photoluminescence. The in situ mask removal may have significant applications in nanopatterned growth processes, where protection of the growth surface from atmospheric exposure reduces surface contamination to improve electrical and radiative interface characteristics. (c) 2005 Elsevier B.V. All rights reserved.