Room-temperature InAs/InAs1−xSbx strained-layer superlattice light-emitting diodes (x∼8%) are reported that emit at λ∼4.2 μm with an internal efficiency of 2.8%. The structures are grown by molecular beam epitaxy on slightly mismatched InAs substrates and include a strained AlSb barrier layer to prevent electron migration to the dislocated substrate–epilayer interface region. Comparison with a near identical structure grown without the barrier layer indicates a factor of four improvement in device efficiency at room temperature.

We have investigated the room-temperature electroluminescent properties of InSb/ Al x In 1−x Sb quantum-well light-emitting diodes. The maximum emission from diodes containing quantum wells occurred at significantly higher energies than the band gap of InSb. Close agreement between experimental and theoretical data confirms that recombination occurs within the quantum well.

Impact of substrate temperature on the structural and optical properties of strain-balanced InAs/InAsSb type-II superlattices grown by molecular beam epitaxy

Infrared (IR) gas sensors are a minority of the general gas-sensing instrument market. They compete with devices based upon gas interaction with surfaces such as electrochemical sensors. They di¬er in that IR devices are selective, can`fail to safety' and are potentially intrinsically safe. However, they tend to be more expensive, using existing technology. We may expect that in due course the impact of all solid-state semiconductor mid-IR technology should revolutionize this situation and lead to signi cant growth in IR gas sensing.

We report the application of optically immersed, room-temperature InSb/InAlSb LED and photodiode devices to the ppm-level detection of nitrogen dioxide (NO2) at a wavelength of 6 µm. The LED emission and the photodiode detectivity are both increased by the optical immersion, resulting in a power dissipation of only 0.25 mW in the LED. A White cell is used for high gas sensitivity and its relatively small numerical aperture can be conveniently matched to the field of view of the hyperspherically immersed devices.

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300 K light-emitting diodes which emit at 5 and 8 μm with quasi-cw output powers of up to 50 and 24 μW, respectively, are reported. The devices have a single molecular beam epitaxy grown InAs/In(As, Sb) quantum well in the active region with a strong type-IIa band alignment giving mid-IR emission at energies up to 64% lower than the alloy band gap. The emission energies are shown to be in good agreement with a k⋅p bandstructure model where Qc, the ratio of the strained conduction-band offset to the band-gap difference between the two strained superlattice components, is found to be ∼2.0.

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