Abstract-AlGaAs/GaAs Terahertz Quantum Cascade Laser with Gold-Based Metal – Metal Waveguide

Anna Szerling, Kamil Kosiel, Piotr Prokaryn, Michał Szymański, Artur Trajnerowicz, Maciej Sakowicz, Piotr Karbownik, Mariusz Płuska, Michał Walczakowski, Norbert Pałka,

https://link.springer.com/chapter/10.1007/978-94-024-1093-8_17

In this chapter, we report the fabrication of Al0.15Ga0.85As/GaAs ~3 THz frequency quantum cascade laser (QCL). Its operation is based on 3-quantum-well (3QW) modules, where the GaAs QWs are separated by Al0.15Ga0.85As barriers. The laser’s active region is build by stacking the 228 modules. The lasers were fabricated as gold-gold waveguide devices and were gold-gold mounted on GaAs receptor wafers. The 300 nm Au/5 nm Ti claddings were made by sputtering, for which we used 8 × 10−3 mbar pressure level and 50 W generator power. The wafer-bonding process was performed in the temperature range 350–400 °C. The structures were wet etched into ridges with widths in the range 50–160 microns and lengths 1.8 mm. The lasers operated with threshold current densities ~650 A/cm2 at 77 K, when fed by 100–300 ns current pulses supplied with 300–1000 Hz repetition frequencies.

Abstract-Processing of AlGaAs/GaAs quantum-cascade structures for terahertz laser

Anna Szerling, Kamil Kosiel, Krystyna Gołaszewska, Adam Łaszcz, Mariusz Płuska, Artur Trajnerowicz, Maciej Sakowicz, Anna Piotrowska

Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw, Poland

Michał Szymański

Warsaw University of Life Sciences, Faculty of Applied Informatics and Mathematics, Nowoursynowska 159, 02-776 Warsaw, Poland

Zbig Wasilewski

University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada

Michał Walczakowski, Norbert Pałka

Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland

Rafał Jakieła

Institute of Physics PAS, Al. Lotników 32/46, 02-668 Warsaw, Poland

J. Nanophoton. 9(1), 093079 (Mar 24, 2015). doi:10.1117/1.JNP.9.093079

http://nanophotonics.spiedigitallibrary.org/article.aspx?articleid=2212285

Abstract.  We report research results with regard to AlGaAs/GaAs structure processing for THz quantum-cascade lasers (QCLs). We focus on the processes of Ti/Au cladding fabrication for metal–metal waveguides and wafer bonding with indium solder. Particular emphasis is placed on optimization of technological parameters for the said processes that result in working devices. A wide range of technological parameters was studied using test structures and the analysis of their electrical, optical, chemical, and mechanical properties performed by electron microscopic techniques, energy dispersive x-ray spectrometry, secondary ion mass spectroscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, and circular transmission line method. On that basis, a set of technological parameters was selected for the fabrication of devices lasing at a maximum temperature of 130 K from AlGaAs/GaAs structures grown by means of molecular beam epitaxy. Their resulting threshold-current densities were on a level of 1.5  kA/cm2. Furthermore, initial stage research regarding fabrication of Cu-based claddings is reported as these are theoretically more promising than the Au-based ones with regard to low-loss waveguide fabrication for THz QCLs.

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