High-quality GaInAs/AlAsSb quantum cascade lasers grown by molecular beam epitaxy in continuous growth mode

Short wavelength (λ<5 μm) quantum cascade lasers are of current interest as they operate in the technologically important atmospheric 3-5 μm transparency window. For this wavelength range the GaInAs/AlAsSb-on-InP material system offers the advantage of a large conduction band offset of about 1.6 eV over the well-established lattice-matched GaInAs/AlInAs-on-InP material combination with a band offset of only 0.5 eV. In this paper, we report on molecular beam epitaxial growth and subsequent structural and compositional analysis of GaInAs/AlAsSb quantum wells as well as quantum cascade laser structures. Special emphasis has been laid on establishing a growth procedure which allows the growth of these structures without growth interruption at the GaInAs/AlAsSb interfaces. The epitaxial layer sequences were analyzed by high-resolution X-ray diffraction, secondary ion mass spectrometry, and transmission electron microscopy. Finally, mesa waveguide GaInAs/AlAsSb QC lasers were fabricated emitting around 4.5 μm, which could be operated in pulsed mode up to 400 K.