SiGeSn-Nanostrukturen für integrierte Quantentopf-Infrarot-Photodetektoren
Zusammenfassung der Projektergebnisse
Spectroscopic sensing in the mid-infrared (MIR, 2-5 μm) and far-infrared (FIR, 5-15 μm) regime utilizes excitations of molecular vibrational and rotational degrees of freedom for high-sensitivity trace detection, chemical emission monitoring, process control, and biological sensing applications. Quantum well infrared photodetectors (QWIP)s capable of covering this spectral range have been successfully fabricated and commercialized based on III-V semiconductor heterostructures (commonly GaAs/AlGaAs), but need to be bonded to the readout electronics, which increases manufacturing cost and can lead to thermal mismatch problems at low operating temperatures. Within this project the aim was to develop and demonstrate the fundamental working principle of group IV-based QWIP sensors which would be CMOS-compatible for integrating sensor and readout circuit. For this purpose a consortium of four partners at the Institute für Halbleitertechnik, Universtät Stuttgart, the department of physics at Humboldt-Universität zu Berlin, and the Leibniz Institut für Innovative Mikroelektronik in Frankfurt/Oder have joined forces to synergistically combine their expertise in growing SixGe1-x-ySny heterostructures, characterizing them using various optical, electronic, and electron-beam-based characterization techniques, and modelling their properties finding self-consistent solutions to a combination of Schrödinger equation and Poisson equation. Molecular beam epitaxy (MBE) was used to a) optimize epitaxy of bulk layers for growth parameter optimization and material characterization and b) device layer epitaxy for the fabrication of SiGeSn (hetero-) devices. Particular focus was on the optimal growth conditions for SiGeSn with high Sn and high Si concentrations. It was, for example, shown that n-type doping concentrations of up to ND = 10^20 cm^-3 in the SiGeSn layers can be achieved and no remarkable segregation effects were observed, making this system suitable for the fabrication of the proposed n-type doped Ge-SiGeSn heterostructures, a prerequisite for the pursued SiGeSn QWIP devices. Also pn diodes comprised of a p-doped Ge layer and a highly doped n-SiGeSn layer, as well as pin diodes were grown and characterized with electroluminescence and photocurrent measurements, but also electrically, using, among others the C-V intercept method. The optimization of growth parameters for these different structures relied also very much on structural characterization and mapping of compositional profiles by TEM and EDX spectroscopy. Highly specialized electron microscopy techniques for mapping band bending at interfaces by inline electron holography and local bandgaps by monochromated low-loss electron energy-loss spectroscopy were also further improved to equip them with the sensitivity required for this work. To improve the understanding of photoluminescence spectra of samples grown within this project, a multivalley effective mass model was developed, which includes the effects of charge separation at the interface through a coupling of the effective mass Schrödinger equation with the Poisson equation and a scheme to solve the coupled equations self-consistently. Based on this solution, those parts of the PL spectra that resulted from phonon-assisted radiative recombination mechanisms were included in a perturbative manner. The final aim of the project, the demonstration of the fundamental working principle of group IV-based QWIP sensors, was not achieved. However, a lot of knowledge has been gained to bring this goal within reach of future research on this topic.
Projektbezogene Publikationen (Auswahl)
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“Electrical characterization of n-doped SiGeSn diodes with high Sn content”, Semiconductor Science and Technology. 33 (2018) 124017
C.J. Clausen, I.A. Fischer, D. Weisshaupt, F. Baerwolf, B. Tillack, G. Colston, M. Myronov, M. Oehme, J. Schulze
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“MBE-Grown SixGe1-x-ySny Diode and Quantum Well Diode Structures with High Sn Content for Optical Applications”, Meeting Abstracts, vol. MA2018-02, no. 31, pp. 1016–1016, Jul. 2018
D. Schwarz, C.J. Clausen, I.A. Fischer, H.S. Funk, M. Oehme, D. Weißhaupt, and J. Schulze
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“SiGeSn material for integrated optical devices”, in: R.G. Baets, P. O’Brien, L. Vivien (Eds.), Silicon Photonics: From Fundamental Research to Manufacturing, SPIE, Strasbourg, France, 2018: p. 11
M. Oehme, D. Schwarz, J. Schulze, C.J. Clausen, I.A. Fischer
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“Temperature stability of MBE-grown SixGe1-x-ySny-structures with high Sn content”. 1st Joint Conference of International SiGe Technology and Device Meeting (ISTDM) and International Conference on Silicon Epitaxy and Heterostructures (ICSi), Potsdam, Germany, May 2018
D. Schwarz, I. A. Fischer, M. Oehme, P. Zaumseil, G. Capellini, and J. Schulze
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„Multi-focus TIE algorithm including partial spatial coherence and overlapping filters“, Optics Express 26 (2018) 11819
A. Eljarrat, J. Müller, M.R.S. Huang, C.T. and Koch
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“Electrical Characterization of Fabricated pin Diodes made from SixGe1-x-ySny with an Embedded Ge1-xSnx Quantum Well”, in 2019 42nd International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), May 2019, pp. 1–6
P. Povolni, D. Schwarz, C.J. Clausen, Y. Elogail, H.S. Funk, M. Oehme, D. Weißhaupt, and J. Schulze
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„Design and application of a relativistic Kramers–Kronig analysis algorithm“, Ultramicroscopy 206 (2019) 112825
A. Eljarrat, C.T. Koch
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“Capacitance-Voltage Measurements on MBE-Grown Ge-SixGe1-x-ySny Heterojunction pn-Diodes for Material Characterisation”, ECS Transactions, vol. 98, no. 5, pp. 339–349, Sep. 2020
D. Schwarz, H. S. Funk, K. Guguieva, M. Oehme, and J. Schulze
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„Alloy Stability of Ge1-xSnx with Sn Concentrations up to 17% Utilizing Low-Temperature Molecular Beam Epitaxy”, Journal of Electronic Materials, vol. 49, no. 9, pp. 5154–5160, Sep. 2020
D. Schwarz, H. S. Funk, M. Oehme, and J. Schulze
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„Composition analysis and transition energies of ultrathin Sn-rich GeSn quantum wells“, Physical Review Materials 4 (2020) 024601
I.A. Fischer, C.J. Clausen, D. Schwarz, P. Zaumseil, G. Capellini, M. Virgilio, M.C. da Silva Figueira, S. Birner, S. Koelling, P.M. Koenraad, M.R.S. Huang, C.T. Koch, T. Wendav, K. Busch, J. and Schulze
