Data are presented characterizing threshold and transverse mode behavior of microcavity lasers, which use a half‐wavelength cavity spacer layer surrounding a single quantum well active region. Selective conversion of AlAs into AlxOyis used to define lateral device dimensions of 2, 5, and 8 &mgr;m. Initial results demonstrate a continuous‐wave room‐temperature lasing threshold current of 97 &mgr;A for a 2 &mgr;m device and 220 &mgr;A for an 8 &mgr;m device. We show that lasing operation is influenced by the AlxOylocated only 200 A˚ from the quantum well. ©1995 American Institute of Physics.