We have studied the wet thermal oxidation ofIn0.52Al0.48Asand its potential application in current and optical confinement in vertical cavity surface emitting lasers (VCSELs). Two types of InP-based heterostructures were used to study the effect of adjacent layer compositions on the lateral oxidation behavior of the InAlAs. It was found that the oxidation ofIn0.52Al0.48Aswith InP adjacent layers, compared withIn0.53Ga0.47Asadjacent layers, proceeded faster, more uniformly and with minimal degradation of the surrounding layers making it ideal for optoelectronic applications. ©1998 American Institute of Physics.