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Open AccessArticle

Optimization of MBE Growth Conditions of In0.52Al0.48As Waveguide Layers for InGaAs/InAlAs/InP Quantum Cascade Lasers

Łukasiewicz Research Network-Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warszawa, Poland
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Materials 2019, 12(10), 1621; https://doi.org/10.3390/ma12101621
Received: 5 May 2019 / Revised: 14 May 2019 / Accepted: 15 May 2019 / Published: 17 May 2019
(This article belongs to the Special Issue Advances in Epitaxial Materials)
We investigate molecular beam epitaxy (MBE) growth conditions of micrometers-thick In0.52Al0.48As designed for waveguide of InGaAs/InAlAs/InP quantum cascade lasers. The effects of growth temperature and V/III ratio on the surface morphology and defect structure were studied. The growth conditions which were developed for the growth of cascaded In0.53Ga0.47As/In0.52Al0.48As active region, e.g., growth temperature of Tg = 520 °C and V/III ratio of 12, turned out to be not optimum for the growth of thick In0.52Al0.48As waveguide layers. It has been observed that, after exceeding ~1 µm thickness, the quality of In0.52Al0.48As layers deteriorates. The in-situ optical reflectometry showed increasing surface roughness caused by defect forming, which was further confirmed by high resolution X-ray reciprocal space mapping, optical microscopy and atomic force microscopy. The presented optimization of growth conditions of In0.52Al0.48As waveguide layer led to the growth of defect free material, with good optical quality. This has been achieved by decreasing the growth temperature to Tg = 480 °C with appropriate increasing V/III ratio. At the same time, the growth conditions of the cascade active region of the laser were left unchanged. The lasers grown using new recipes have shown lower threshold currents and improved slope efficiency. We relate this performance improvement to reduction of the electron scattering on the interface roughness and decreased waveguide absorption losses. View Full-Text
Keywords: InAlAs; molecular beam epitaxy; surface morphology; quantum cascade lasers; X-ray spectroscopy InAlAs; molecular beam epitaxy; surface morphology; quantum cascade lasers; X-ray spectroscopy
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Gutowski, P.; Sankowska, I.; Słupiński, T.; Pierścińska, D.; Pierściński, K.; Kuźmicz, A.; Gołaszewska-Malec, K.; Bugajski, M. Optimization of MBE Growth Conditions of In0.52Al0.48As Waveguide Layers for InGaAs/InAlAs/InP Quantum Cascade Lasers. Materials 2019, 12, 1621.

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