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GaAs-based, single-stage, intersubband devices with active regions composed of deep quantum wells (i.e., In0.3Ga0.7As) and high AlGaAs harriers display strong room-temperature emission at λ = 4.7 µm. The structures are grown by metalorganic chemical vapor deposition. The large energy harriers (∼360 meV) for electrons in the upper energy level of the active region strongly suppress both the carrier leakage as well as the tunneling escape rate out of the wells. As a result, the ratio of emissions at 80 and 300 K is as low as 2.0, and thus there is considerably less need for a Bragg mirror/transmitter-type region. Devices with virtually 100% tunneling injection efficiency have been realized, and their room-temperature spectra are narrow: 25 meV full width at half maximum. These deep-well, single-stage structures are intended for use as the emitting units in two-dimensional, intersubband quantum-box lasers, or as the stages of quantum-cascade lasers for efficient, room-temperature operation in the 3-5-µm wavelength range. [ABSTRACT FROM AUTHOR]