Intrinsic optical confinement and lasing in InAs–AlGaAs submonolayer superlattices

We study the optical properties of structures composed of stacked InAs submonolayer insertions in an AlGaAs matrix grown on a GaAs(100) surface. The increased refractive index in the active region necessary for waveguiding is caused by the absorption peak due to excitons trapped by monolayer-height InAs islands. Despite a very low average InAs concentration, a thin AlGaAs buffer layer and an absorbing GaAs substrate photopumped lasing in the visible spectral range is already realized at low excitation density.