Mid-infrared resonant cavity light emitting diodes operating at 4.5 µm

We report on a mid-infrared resonant cavity light emitting diode (RCLED) operating at the wavelength of 4.5 µm with a narrow spectral linewidth at room temperature. Compared to a reference LED without a resonant cavity, our RCLED exhibits (85x) higher peak intensity, (13x) higher integrated output power, (16x) narrower spectral linewidth and (7x) superior temperature stability. The device consists of a one-wavelength thick micro-cavity containing an Al_0.12In_0.88As/InAs_0.85Sb_0.15 quantum well active region sandwiched between two high contrast AlAs_0.08Sb_0.92/GaSb distributed Bragg reflector mirrors, grown lattice-matched on GaSb by molecular beam epitaxy. The high spectral brightness, narrow linewidth and superior temperature stability are attractive features, enabling these devices to be used for detection of N₂O at 4.5 µm. We show that with only minor adjustments the gases CO₂ (4.2 µm) and CO (4.6 µm) are also readily accessible.