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8 March 2019 AlGaAs/GaAs terahertz quantum cascade lasers with copper waveguides (Conference Presentation)
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Abstract
Fabrication of approx. 3 THz Al0.15Ga0.85As/GaAs QCLs grown by Molecular Beam Epitaxy equipped with Ta/Cu or Ti/Cu waveguide claddings will be presented. Our previous studies showed that copper layers as the waveguide claddings are most promising in THz QCLs technology. The theoretical predictions showed that lasers with Ti/Cu or Ta/Cu claddings (where Ti and Ta play the role of diffusion barriers and improve adhesion) show the smallest waveguide losses when compared with other metals. The main important issue of the presentation will be the wafer bonding of the QCL active region and GaAs receptor wafer. We will compare the results of ex-situ and in-situ bonding technology. The structures were tested by optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS). Our studies show that it was necessary to apply at least 5 nm-thick diffusion-barrier layers, as well as to keep all of the process temperatures below 400C in order to ensure the barrier tightness. The next important issue was control of composition of metallic claddings, in order to provide the control of the refractive index profiles of the claddings. The ridge structure lasers were fabricated with ridge width in the range 100 – 140 µm, formed by dry plasma etching in BCl3/Cl2/Ar mixture in ICP RIE system. The lasers operated with threshold current densities of approx. 1.2 kA/cm2 at 77 K and the Tmax = 130 K, when fed by 100-300 ns current pulses supplied with 0.3-1 kHz repetition frequencies. *This research is supported by The National Centre for Research and Development (bilateral cooperation, project no. 1/POLTUR-1/2016) and TUBITAK (Scientific and Technical Research Council of Turkey) project number 215E113.
Conference Presentation
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Anna Szerling, Kamil Kosiel, Piotr Prokaryn, Renata Kruszka, Jacek Ratajczak, Krystyna Golaszewska-Malec, Maciej Sakowicz, Zbig Wasilewski, Michał Szymański, Maciej Kuc, Tomasz Czyszanowski, Mehtap Özdemir Köklü, Gülnur Aygün, Lütfi Özyüzer, and Norbert Pałka "AlGaAs/GaAs terahertz quantum cascade lasers with copper waveguides (Conference Presentation)", Proc. SPIE 10926, Quantum Sensing and Nano Electronics and Photonics XVI, 109261I (8 March 2019); https://doi.org/10.1117/12.2510489
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