Gela Kipshidze

Continuous wave operation of diode lasers at 3.36μm at 12°C

GaSb-based type-I quantum-well diode lasers emitting at 3.36μm at 12°C with 15mW of continuous wave output power are reported. Devices with two or four InGaAsSb compressively strained quantum wells and AlInGaAsSb quinternary barriers were fabricated and characterized. It was shown that increase in the quantum-well number led to improved laser differential gain and reduced threshold current.

Type-I Diode Lasers for Spectral Region Above 3 μm

In this paper, we consider the role of carrier confinement in achieving high-power continuous wave (CW) room temperature operation of GaSb-based type-I quantum-well (QW) diode lasers at wavelengths above 3 μm. The use of compressive strain and quinternary barrier materials to confine holes in the active QWs allows the fabrication of 3-μm GaSb-based type-I QW diode lasers operating at 17 °C in the CW mode with output power of 360 mW. We will present the results of characterization of 2.2-μm diode lasers grown on metamorphic virtual substrates. The use of InGaSb virtual substrate makes it possible to fabricate devices with As free QWs. The prospects of using virtual substrates for development of GaSb-based type-I lasers will be discussed.

Continuous-wave room temperature operated 3.0μm type I GaSb-based lasers with quinternary AlInGaAsSb barriers

Diode lasers emitting at 3.0μm were designed and fabricated. Device active region contained two compressively strained InGaAsSb quantum wells incorporated in quinternary AlInGaAsSb barriers. Laser output power at room temperature was 130mW in continuous wave regime and more than 1W in pulse.

Room temperature operated 3.1μm type-I GaSb-based diode lasers with 80mW continuous-wave output power

High-power diode lasers with heavily-strained In(Al)GaAsSb type-I quantum-well active region emitting at 3.1 mum at room temperature are reported. Devices operate in continuous-wave regime with output power above 200 mW and 80 mW at 250 K and 285 K, correspondingly.

Properties of unrelaxed InAs1−XSbX alloys grown on compositionally graded buffers

Unrelaxed InAs1−xSbx layers with lattice constants up to 2.1% larger than that of GaSb substrates were grown by molecular beam epitaxy on GaInSb and AlGaInSb compositionally graded buffer layers. The topmost section of the buffers was unrelaxed but strained. The in-plane lattice constant of the top buffer layer was grown to be equal to the lattice constant of unrelaxed and unstrained InAs1−xSbx with given X. The InAs0.56Sb0.44 layers demonstrate photoluminescence peak at 9.4 μm at 150 K. The minority carrier lifetime measured at 77 K for InAs0.8Sb0.2 was τ = 250 ns.

Type-I GaSb-Based Laser Diodes Operating in 3.1- to 3.3-

Type-I quantum-well (QW) diode lasers based on AlInGaAsSb-InGaAsSb-AlInGaAsSb heterostructure active region with narrow waveguide and high indium content in the barrier were fabricated. Room-temperature continuous-wave output power of 190, 165, and 50 mW for devices emitting 3.1, 3.2, and 3.3 μm correspondingly were demonstrated. Experiment shows that improvement of the hole confinement in QWs by use of 32% indium in AlGaInAsSb barrier is a promising way of further enhancement of the device performance.

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Metamorphic heterostructures containing bulk InAs1−xSbx layers and AlInAsSb barriers were grown on GaSb substrates. The lattice mismatch (up to 2.1%) between the GaSb substrates and the InAsSb layers was accommodated by the growth of GaInSb linearly graded buffers. The 1 μm thick InAsSb0.44 layer with an absorption edge above 9 μm exhibited an in-plane residual strain of about 0.08%. InAs1−xSbx structures with x = 0.2 and x = 0.44 operated as light emitting diodes at 80 K demonstrated output powers of 90 μW and 8 μW at 5 μm and 8 μm, respectively.

m Wavelength Range

GaInSb and AlGaInSb compositionally graded buffer layers grown on GaSb by MBE were used to develop unrelaxed InAs1-XSbXepilayers with lattice constants up to 2.1 % larger than that of GaSb. The InAsSb buffer layer was used to grow InAs0.12Sb0.88 layer on InSb. The structural and optical characterization of 1-μm thick InAs1-xSbx layers was performed together with measurements of the carrier lifetime.

Metamorphic InAsSb/AlInAsSb heterostructures for optoelectronic applications

The cascade pumping scheme reduced the threshold current density of high power type-I quantum well GaSb-based λ ∼ 3 μm diode lasers down to ∼100 A/cm2 at room temperature. Laser heterostructures had single GaInAsSb quantum well gain stages connected in series by means of GaSb/AlSb/InAs tunnel junctions followed by InAs/AlSb electron injectors. Devices with densely stacked two and three gain stages and 100-μm-wide aperture demonstrated peak power conversion efficiency of 16% and continuous wave output power of 960 mW. Corresponding narrow ridge lasers demonstrated above 100 mW of output power. The experiment showed that the bandwidth of the gain and its rate of increase with current depended strongly on the thickness of AlSb layer separating electron injectors from quantum wells. The possible impact of electron injector interfaces and ionized impurities on the carrier scattering and recombination in the active quantum well is discussed.

Effects of carrier concentration and phonon energy on carrier lifetime in Type-2 SLS and properties of InAs 1-X Sb X alloys

InAs0.6Sb0.4/Al0.75In0.25Sb-based barrier photodetectors were grown metamorphically on compositionally graded Ga1−xInxSb buffer layers and GaSb substrates by molecular beam epitaxy. At the wavelength of 8 μm and T = 150 K, devices with 1-μm thick absorbers demonstrated an external quantum efficiency of 18% under a bias voltage of 0.45 V.