Mid-infrared-emitting Quantum Cascade Lasers on Metamorphic Buffer Layers

Download or read book Mid-infrared-emitting Quantum Cascade Lasers on Metamorphic Buffer Layers written by Ayushi Rajeev and published by . This book was released on 2019 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: When using conventional substrates, such as InP and GaAs, the materials constituting the superlattice (SL) core region of the quantum cascade laser (QCL) are constrained by strain-induced critical-thickness limitations. Metamorphic buffer layers (MBLs) can serve as "virtual substrates" with a designer-chosen surface lattice constant, thus expanding the compositional-design space for a variety of device structures, including short-wavelength QCLs. An optimized short-wavelength (3.4 [mu]m) single-phonon-resonant (SPR)+ miniband extraction QCL design, grown on an [InxGa1-xAs] MBL, is presented along with the optical and thermal device considerations in play. MBLs can be grown with a variety of graded regions such as linear composition grade from GaAs to [InxGa1-xAs] or by employing dislocation filters between Si substrate and InP. QCL and test superlattices' regrowth on these MBLs with the corresponding materials and device analysis, is presented in this work. In addition to the materials limitation for the design of QCL devices, the requirement to have the constituent layers (1-5 nm) to be precisely controlled in the various compositions and thicknesses, is a challenge. Interfacial grading in strained SLs is studied via atom probe tomography for SLs with various layer thicknesses and relative lattice strains. The tip reconstructions are analyzed by fitting the interfaces to diffusion profiles. Mechanisms possible for the observed interdiffusion profile, such as surface segregation and/or bulk diffusion, are discussed. With an understanding of the compositional gradient at the interfaces, together with optimized QCL designs and regrowth on the MBLs, short-wavelength QCLs with high performances can be achieved.