Resonant cavity interband cascade light-emitting devices operating beyond 4 µm with high spectral intensity

We report the growth, fabrication, and characterization of resonant cavity interband cascade light-emitting devices (RCICLEDs), and compare their performance to the best previous results for midwave infrared (MW) LEDs and resonant cavity LEDs. A cavity with a high quality factor (> 400) was realized by bonding the GaSb-based ICLED structure, with 20 stages divided into two groups placed at antinodes of the resonant cavity, to a GaAs-AlGaAs distributed Bragg reflector (DBR) with reflectivity > 99%, and then depositing a single-period SiO₂/Ge DBR on top. Circular mesas were processed as full-cavity (with both top and bottom DBRs) and half-cavity (with only the bottom DBR) devices. Spectral characterization finds that the full-cavity RCICLED emits primarily within a narrow spectral resonance with a linewidth of 40 nm centered on 4.47 µm, which compares to ≈ a 1000 nm linewidth for a reference ICLED processed from a similar wafer without a resonant cavity. At a relatively low injection current density of 110 A/cm², the total emittance from the full-cavity device is 0.91 W/cm², while the portion contained within the cavity resonance is estimated as ≈ 0.64 W/cm². The present results are compared to the best previously-reported room-temperature values for emittance, wallplug efficiency, spectral bandwidth, and spectral intensity for MW LEDs and RCLEDs from the literature. For cw operation, the present half-cavity device displays higher emittance than any previous result for high-duty-cycle operation without an immersion lens at a wavelength longer than 3.3 µm. The wallplug efficiency for the full-cavity device is higher than any previously-reported result for an MW RCLED operating under conditions that produce high spectral intensity, and it displays higher emittance, narrower linewidth, and higher spectral intensity than any previous device emitting at a wavelength longer than 3.3 µm. We conclude that the present approach to narrow-band emission will be very attractive in applications like chemical sensing and infrared scene projection.