We report a complete fabrication process of InAs/GaSb type-II superlattice long-wavelength infrared photodiodes with band structure modelling, materials growth and device fabrication. The optoelectronic property of InAs/GaSb type-II superlattices is simulated by the modified empirical tight binding model for interface stoichiometry. We chose target superlattices from the simulation results. To obtain good lattice matched and high interface quality material, a two-step strain balance method of migration-enhanced epitaxy is applied in the growth of superlattices. The property of superlattices is matched well with the simulation results. Finally, photodiodes with 50% cutoff wavelength of 8.72 µm and peak detectivity of 8.1 × 1010 cm Hz1/2 W−1 at 77 K are demonstrated.
GaSb-based 2.4 𝜇m InGaAsSb/AlGaAsSb type-I quantum-well laser diode is fabricated. The laser is designed consisting of three In0.35Ga0.65As0.1Sb0.9/Al0.35Ga0.65As0.02Sb0.98 quantum wells with 1% compressive strain located in the central part of an undoped Al0.35Ga0.65As0.02Sb0.98 waveguide layer. The output power of the laser with a 50-𝜇m-wide 1-mm-long cavity is 28 mW, and the threshold current density is 400 A/cm 2 under continuous wave operation mode at room temperature.
InAs/AlSb deep quantum well (QW) structures with high electron mobility were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates. AlSb and Al0.75Ga0.25Sb buffer layers were grown to accommodate the lattice mismatch (7%) between the InAs/AlSb QW active region and GaAs substrate. Transmission electron microscopy shows abrupt interface and atomic force microscopy measurements display smooth surface morphology. Growth conditions of AlSb and Al0.75Ga0.25Sb buffer were optimized. Al0.75Ga0.25Sb is better than AlSb as a buffer layer as indicated. The sample with optimal Al0.75Ga0.25Sb buffer layer shows a smooth surface morphology with root-mean-square roughness of 6.67 Å. The electron mobility has reached as high as 27 000 cm2/Vs with a sheet density of 4.54 × 1011/cm2 at room temperature.
We report a type-I GaSb-based laterally coupled distributed-feedback (LC-DFB) laser with shallow-etched gratings operating a continuous wave at room temperature without re-growth process. Second-order Bragg gratings are fabricated alongside the ridge waveguide by interference lithography. Index-coupled LC-DFB laser with a cavity of 1500 µm achieves single longitudinal mode continuous-wave operation at 20 • C with side mode suppression ratio (SMSR) as high as 24 dB. The maximum single mode continuous-wave output power is about 10 mW at room temperature (uncoated facet). A low threshold current density of 230 A/cm 2 is achieved with differential quantum efficiency estimated to be 93 mW/A. The laser shows a good wavelength stability against drive current and working temperature.
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