Tunable interminiband infrared emission in superlattice electron transport

The observation of infrared emission between superlattice conduction minibands is reported. Electrons resonantly injected into the first excited state miniband by an applied electric field make a radiative transition to the ground state miniband. The spectra are dominated by direct high oscillator strength transitions at the mini-Brillouin zone edge and the peak wavelength can be tailored over a broad infrared range by designing the superlattice minigap. At high bias, the spectra extend to wavelengths corresponding to transitions from high lying states near the mini-Brillouin zone center. Experiments in AlInAs/GaInAs superlattices have demonstrated peak luminescence wavelengths of λ=5 and 7 μm. At high currents, the spectra broaden to shorter wavelengths (down to 3 μm) as electrons are tunnel injected high into the second miniband.