Room temperature InAs/InAs1-xSbx single quantum well light emitting diodes with barriers for improved carrier confinement

Room temperature InAs/InAs_1-xSb_x single quantum well light emitting diodes for the mid-infrared region that emit at λ~4.2 μm with an internal efficiency of 2.6% and pulsed output powers of more than 110 μW/A are studied. The structures are grown by molecular beam epitaxy and include an InAl_0.17As_0.83 barrier for enhanced electron confinement in the active region. Comparison with an identical structure grown without the barrier demonstrates an improvement in room temperature efficiency by a factor of more than six. Additional magneto-electroluminescence measurements reveal several very narrow subband transitions with a typical FWHM of only 10 meV. The broad (~40 meV) LED emission spectra are therefore due to multiple bound states in the quantum wells. This shows the high material quality of the quantum wells, and that the quasi-Fermi energy separation, even at low (150 A/cm ²) current densities, exceeds ~30 meV and promises excellent prospects for high gain in laser diode structures made from these heterostructures