Data are presented on the photopumped laser operation of planar AlAs–GaAs superlattice (SL) minidisk lasers. The SL minidisk (70 A˚ AlAs, 30 A˚ GaAs; 100 periods; ∼37 &mgr;m diameter) is defined by impurity‐induced layer disordering (IILD), followed by wet oxidation (N2+H2O vapor, 400 °C which surrounds the minidisk with a low‐refractive‐index AlGaAs oxide. The planar minidisks exhibit laser operation at &lgr;∼7540 A˚, with wider mode separation (&Dgr;&lgr;∼13 A˚) than disks defined by only IILD (a smaller refractive index step) and cleaved sample edges. The mode separation of &Dgr;&lgr;∼13 A˚ corresponds to disk modes that utilize the perimeter of the oxide‐defined disks. In the fabrication of the SL minidisks, IILD forms a structural and doping difference beyond the disk perimeter that acts, in effect, as ap–njunction during etching or wet oxidation. Etch profiles are shown demonstrating this behavior. ©1996 American Institute of Physics.