Electrically tunable mid-infrared electroluminescence from graded cascade structures

Mid-infrared electroluminescence (EL) is observed from multiperiod bilayer type-II InAs/AlGaSb structures with the effective interlayer separation controlled by bias. The emission with powers in the microwatt range is characterized by a linear dependence of the photon energy on the bias. By measuring the temperature and current dependence of EL, we find evidence that the EL emission results from recombination of holes in AlGaSb quantum wells (QWs) with electrons occupying two different quantum states in InAs QWs.