Electroluminescent devices have been fabricated by depositing Al-doped ZnSTe onto GaAs substrates by molecular beam epitaxy. A moderately bright blue-light emission was observed at room temperature. Electroluminescence spectra reveal that light emission is mostly from impact excitation of Te isoelectronic centers in these structures. Surface morphologies and concurrent current images by using conducting atomic force microscopy indicate electrical inhomogeneity in such structures. Nonuniform light emission may be inferred from nonuniform current distributions on the submicrometer scale.