Quantum-dot LEDs exhibit mid-IR emission at room temperature

While quantum-dot (QD)-based light-emitting diodes (LEDs) have made much progress recently, few reports exist of success at mid-infrared (mid-IR) wavelengths, despite their promise for improved efficiency and narrower spectral linewidth compared to quantum-well devices. Physicists at Lancaster University (Lancaster, England) and at the Ioffe Physico-Technical Institute (St. Petersburg, Russia) have reported intense photoluminescence at a peak of 3.8 µm from indium antimonide/indium arsenide (InSb/InAs) quantum-dot LEDs. The structures were grown by molecular-beam epitaxy using Sb₂ and As₂ fluxes, which overcome problems with growth interruptions to Sb₄ flux during growth. The growth temperature was varied between 300°C and 450°C to determine the InSb QD layer thickness.

The most efficient LED, with an internal nonoptimized quantum efficiency of 0.4%, was composed of larger dots formed at 430°C, with a monolayer of InSb. An undoped 30-nm-thick electron-blocking alloy of aluminum, gallium, arsenide, and antimonide further increased the room-temperature electroluminescence intensity by a factor of five. The LED had an output power of 6 µW, which the team says could be significantly improved with optimization. Contact Anthony Krier at [email protected].