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A design for midinfrared diode lasers based on interband type-II miniband-to-bound state transitions is proposed and has been demonstrated experimentally. Type-II miniband-to-bound state laser structures emitting at 3.25 mu with active regions consisting of 5 and 10 W periods were grown by solid-source molecular-beam epitaxy and processed into ridge waveguide lasers. Substrate-side down mounted devices with a 10 period active region and uncoated facets could be operated in continuous-wave (cw) mode up to 185 K and as high as 260 K in pulsed mode. A high characteristic temperature of 100 K has been achieved for heat-sink temperatures below 140 K, decreasing to 33 K for the 140 to 185 K interval. At 110 K, a 5 period laser structure exhibited a threshold current density of 177 A/cm2and a slope efficiency of 61 mW/A. Single-ended output powers of 144 mW in cw mode and exceeding 330 mW in pulsed operation were obtained for a substrate-side down mounted 5 period diode laser with high-reflection/antireflection coated mirror facets, operated at 110 K.

High-power high-brightness 1.93-µm wavelength (AlGaIn)(AsSb) tapered diode lasers with a narrow vertical waveguide design are reported for the first time. A nearly diffraction-limited continuous-wave output power of 1.5 W together with a remarkable low fast axis divergence of 43° full-width at half-maximum have been demonstrated. The maximum brightness amounts to 32 MW/cm2 sr.

The influence of strain in Ga(0.7)In(0.3)As(y)Sb(1-y) quantum wells (QWs) embedded in Al(0.24)Ga(0.76)As(y)Sb(1-Y) barriers on the photoluminescence (PL) emission wavelength and intensity has been investigated. The strain was adjusted by varying the As content in the QW and barrier layers. For As mole fractions in the (GaIn)(AsSb) QW layers between y = 0.25 and 0.05, the average strain perpendicular to the growth plane changes from (delta a/a) = 2.0 x 10(exp -3) to 10.4 x 10(exp -3) for lattice matched (AlGa)(AsSb) barriers. At room temperature, highest PL intensities are obtained for QW structures with a net compressive strain of (delta a/a) = 8.7 x 10(exp -3). In order to compensate the compressive strain in the QWs, strain-balanced laser core structures with barriers under tensile strain have been investigated. This was found to allow a reduction of the average strain in the laser core without shifting its emission wavelength. Ridge waveguide large optical cavity (LOC) laser diodes containing three compressively strained (Galn)(AsSb) QWs embedded between lattice matched (AlGa)(AsSb) barriers show room temperature cw laser emission at a wavelength of 2.26 mu m. For 64 mu m wide and 600 mu m long devices, a differential quantum efficiency of 43% and a threshold current density of 395 A/cm2 with a characteristic temperature of T(0) = 110 K are obtained.

The incorporation of As and In during MBE growth in (AlGaIn)/(AsSb) layers used for the fabrication of diode lasers in the 2.0-2.5 mu m wavelength range has been investigated. The As content was found to depend linearly on the beam equivalent pressure for As mole fractions between y = 0.05 and y = 0.20. Broad area A1GaAsSb/GaInAsSb singlequantum well laser diodes with quasi-cw output at room temperature at an emission wavelength of 2.03 mu m and a threshold current density of 515 A/cm2 for 1370 mu m long and 70 mu m wide devices have been fabricated. In order to shift the emission wavelength of the laser structures to longer wavelengths, the growth of lattice matched AlGaAsSb/ GaInAsSb laser core structures with different In and As mole fractions in the quantum wells has been investigated.