We have investigated the propel ties of type-II bilayer quantum-well structures grown by molecular-beam epitaxy for use in long-wavelength lasers on GaAs substrates. Structures with layer strains acid thicknesses designed to be thermodynamically stable against dislocation formation exhibit room-temperature photoluminescence at wavelengths as long as 1.43 mu m. The photolumincscence emission wavelength is significantly affected by growth temperature and the sequence of layer growth (InGaAs/GaAsSb versus GaAsSb/InGaAs), suggesting that Sb and/or In segregation results in nonideal interfaces under certain growth conditions. At low-injection currents, double-heterostructure lasers with CaAsSb/InGaAs bilayer quantum-well active regions display electroluminescence at wavelengths comparable to those obtained in photoluminescence, but at higher currents the electroluminescence shifts to shorter wavelengths. Lasers have been obtained with threshold current densities of 120 A/cm(2) at 1.17 mu m, and 2.1 kA/cm(2) and 2.1 mu m.