Broadband Midwave Infrared InAs/GaSb Superlattice Light-Emitting Diodes

Broadband (3.0 $\mu $m to 5.0 $\mu $m) emission is reported from InAs/GaSb superlattice light-emitting diodes grown via molecular beam epitaxy . Stacked active regions, each with a different emission wavelength, were connected with tunnel junctions, resulting in multiple emission wavelengths in a monolithic structure. Eight active regions provided eight overlapping emission spectra, simulating a broadband spectrum. Chips with mesas of sizes ranging from 24 $\mu $m x 24 $\mu $m to 400 $\mu $m x 400 $\mu $m were fabricated and wire bonded to a leadless chip carrier (LCC). The LCC was mounted in a liquid nitrogen cryostat. At low input currents, distinct peaks were observed at 3.3 $\mu $m, 3.6 $\mu $m, 3.9 $\mu $m, 4.2 $\mu $m, 4.5 $\mu $m, 4.9 $\mu $m, and 5.3 $\mu $m. At high input currents a continuous spectrum was observed with a peak near 3.8 $\mu $m and with a full-width at half-maximum of 1.42 $\mu $m. In quasi-continuous operation at 77 K, radiances exceeding 0.35 W/cm$^{\mathrm{2}}$-sr in a Lambertian profile were achieved. Current dependent electroluminescent spectra measured at liquid nitrogen temperatures demonstrate the blending of the various colors from each stage into one smooth spectrum at high currents.