Script list Publications
(1) 230 - 330 GHz Microstrip Leaky-Wave Antenna Array using BiCMOS BEOL Silicon Interposer
A. Bhutani, J. Yin, E. Bekker, J. Dittmer, J. Blank, K. Joy, P. Krüger, T. Voß, C. Carta, M. Wietstruck, T. Zwick
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(ESSENCE-6GM)
(2) Ultra-Broadband Photonic Signal-Processor
N. Hanik, T. Kernetzky, U. Höfler, Y. Jia, C. Schubert, M. Karvar, I. Sackey, R. Freund, G. Ronniger, L. Zimmermann
Electronic-Photonic Integrated Systems for Ultrafast Signal Processing, 1st Edition, Editors: J.C. Scheytt, C. Kress, M. Berroth, S. Pachnicke, J. Witzens, Chapter 1. Ultra-Broadband Photonic Signal-Processor, Springer, 1 (2026)
DOI: 10.1007/978-3-032-08340-1_1
(3) Design and Characterization of a Differential UWB LNA Intended for Space Applications
A. Harneer Suresh, G. Fischer, D. Martynenko, F. Korndörfer, C. Carta
Proc. 17th German Microwave Conference (GeMiC 2026), (2026)
(AMX IP)
(4) A Compact Differential DC-203 GHz Variable-Gain Amplifier in a 130-nm SiGe BiCMOS Technology
T. Herbel, C. Heine, M. Wietstruck, D. Kissinger
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(5) Micro-Transfer Printing of SiGe BiCMOS Electronic Chiplets on Silicon
H. Li, T. Pannier, Y. Gu, P. Ramaswamy, R. Loi, P. Heise, M. Inac, A. Farrell, A.J. Trindade, A. Fecioru, K. Dhaenens, T. De Baere, N. Singh, L. Bogaert, S. Qin, B. Pan, J. Zhang, G. Van Steenberge, P. Ossieur, G. Roelkens
IEEE Journal of Selected Topics in Quantum Electronics 32(2), 6000208 (2026)
DOI: 10.1109/JSTQE.2026.3664420
We demonstrate micro-transfer printing (μTP) and post-printing metallization of thin electronic chiplets on silicon, with a view to heterogeneously integrate electronic integrated circuits (EICs) with photonic integrated circuits (PICs). μTP decouples the fabrication of EICs and PICs, and simultaneously enables their tight integration with high-throughput, small form-factor and on wafer-scale. In this study, we successfully established the process flow for releasing and printing 300 μm × 200 μm SiGe BiCMOS electronic driver chiplets and electrically connecting these chiplets using a polymer ramp to overcome the 20-μm chiplet thickness, providing a gain of 14 dB and bandwidth of over 35 GHz with low-parasitic interconnections. The proposed methodology provides a practical and mass-producible solution to realize the stacking of EICs on silicon photonic wafers for emerging applications such as co-packaged optics (CPO).
(6) Electroluminescence and Franz-Keldysh Modulation Observed in Sn/Ge Multi-Quantum Wells
M. Oehme, D. Marian, M. Wanitzek, C. Spieth, D. Schwarz, F. Bärwolf, M.A. Schubert, A. Daus, M. Virgilio, G. Capellini
Advanced Optical Materials 14(9), e03561 (2026)
DOI: 10.1002/adom.202503561, (IHP- Roma Tre University Joint Lab)
Thanks to their tunable electronic and optical properties, GeSn alloys have emerged as promising materials for next-generation silicon-compatible optoelectronic devices operating at extended near- to mid-infrared wavelengths. In this work, we experimentally and theoretically investigate the optoelectronic properties of p-type/intrinsic/n-type (PIN) diodes based on ultrathin α-Sn/Ge multiple quantum well (MQW) structures grown by molecular beam epitaxy with different Ge barrier thicknesses. Thorough structural analysis confirms the high crystalline quality of the MQW and clearly defined interfaces with Sn contents in the wells exceeding 4 at.%. Room-temperature electroluminescence measurements reveal two direct transitions: an MQW stack independent higher-energy emission, related to direct radiative recombination in intrinsic Ge, and a Ge barrier-dependent lower-energy peak, attributed to transitions involving weakly quantum-confined states, whose energy shifts with the barrier thickness in agreement with theoretical prediction. In line with this observation, the devices exhibit clear signatures of the Franz–Keldysh effect when operated as photodetectors, in a wavelength range extending well beyond the direct gap of Ge, as captured by theoretical modeling. These results demonstrate the potential of α-Sn/Ge MQWs as an integrable material platform for complementary metal—oxide–semiconductor (CMOS)-compatible electro-optical modulators spanning the near- to mid-infrared range.
(7) Influence of Illumination Conditions on Photoluminescence Enhancement in an Al/Si/Ge Metasurface
P. Oleynik, D. Ryzhak, J. Schlipf, C.A. Chavarin, Y. Yamamoto, F. Berkmann, M. Ratzke, I.A. Fischer
Optics Express 34(1), 78 (2026)
DOI: 10.1364/OE.577751
Strong field enhancement supported by metasurfaces at resonance can be used to control and enhance the spontaneous emission rate of emitters. This is particularly relevant for emitters with comparatively low quantum yield such as germanium. Here, we investigate the µ-photoluminescence response obtained from a hybrid metasurface comprising a square lattice of Al/Si/Ge pillars. We explore how variations in excitation energy, excitation intensity and number of excited meta-atoms affect the spectral dependence of the photoluminescence signal and, in particular, the contribution of the metasurface to it. Our metasurface exhibits a magnetic dipole collective lattice resonance, whose contribution to the photoluminescence signal increases with increasing number of excited meta-atoms. Measuring only one metasurface under different illumination conditions can potentially be an alternative approach to probe the transition between finite-size effects and collective effects.
(8) X-Ray Characterization of Multilayered SiGe Nanodots Depending on the Si Spacer Growth Temperature
R. Suenaga, Y. Ito, W.-C. Wen, Y. Yamamoto, N. Sawamoto, K. Omote, A. Ogura
Materials Science in Semiconductor Processing 208, 110553 (2026)
DOI: 10.1016/j.mssp.2026.110553
SiGe nanodots (NDs) are attractive materials because of their potential for optoelectronic device applications and their high compatibility with Si-based semiconductor technologies. To develop SiGe NDs as effective optoelectronic devices, it is crucial to characterize the SiGe composition and strain to understand their band structure. In this paper, we present the characterization of SiGe NDs/Si spacer multilayered structures with different Si spacer growth temperatures using lab-based X-ray diffraction (XRD) and reciprocal space mapping (RSM). The RSM determined the spatial arrangement and Ge content of the SiGe NDs. The results showed a decrease in Ge content in the SiGe NDs as the Si spacer growth temperature increased. In-plane XRD measurements revealed the coexistence of tensile- and compressively strained regions within the SiGe NDs and Si spacers, with the proportion of strained regions increasing at higher Si spacer growth temperatures. The calculated bandgap energy of the type-II heterointerface between the Si spacer and SiGe NDs, based on the SiGe composition and strain states determined by XRD and RSM, aligns well with the previously reported blue shift in photoluminescence as the Si spacer growth temperature increased.
(9) A Bidirectional Shunt-Switch D-Band Mixer with a Double-Balanced Combining-Filter in a 130-nm BiCMOS Technology
A. Tiefenbach, L. Zimmermann, D. Kissinger
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(10) Monolithically Integrated Optical Through-Silicon Waveguides for 3D Chip-to-Chip Photonic Interconnects
F. Villasmunta, P. Heise, M. Breiter, S. Schrader, H. Schenk, M. Regehly, A. Mai
IEEE Journal of Selected Topics in Quantum Electronics 32(2), 3700215 (2026)
DOI: 10.1109/JSTQE.2025.3615001
The scaling limitations of electrical interconnects are driving the demand for efficient optical chip-to-chip links. We report the first monolithic integration of air-clad optical through-silicon waveguides in silicon, fabricated via Bosch and cryogenic deep reactive-ion etching. Rib, single-bridge, and double-bridge designs with 50 μm cores and up to 150 μm propagation lengths have been evaluated. Cryogenic-etched rib waveguides achieve the highest median transmission (66%, −1.80 dB), compared to Bosch-etched ribs (62%, −2.08 dB). Across all geometries, 3 dB alignment windows range from 9.3 μm to 49.2 μm, with Bosch-etched double-bridge waveguides providing the broadest tolerance. We show that geometric fidelity outweighs sidewall roughness for transmission and alignment in these large-core, multimode optical through-silicon waveguides. This technology provides a scalable, complementary metal-oxide semiconductor-compatible pathway toward 3D photonic interconnects.
(11) Silicon Interposer with Advanced RF Technology Modules for BiCMOS Wafer-Level Packaging
M. Wietstruck, P. Krüger, T. Voß, S. Schulze, M.F. Bashir, S. Tolunay Wipf, E.C. Durmaz, K. Joy, N. Hasnayen, B. Sütbas
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(ESSENCE-6GM)
(12) Atomic Layer Epitaxy of Si in Ge
Y. Yamamoto, W.-C. Wen, F. Bärwolf, M.A. Schubert:, D. Steckler, J. Murota, B. Tillack
Japanese Journal of Applied Physics 65(1), 01SP02 (2026)
DOI: 10.35848/1347-4065/ae2c94, (Photonics)
Atomic-layer epitaxy (ALE) of Si in Ge using SiH2Cl2 (DCS) is investigated by a cyclic process of selective Ge epitaxy and DCS exposure using chemical vapor deposition. Steep Si profile < 0.6 nm/dec. is realized by the DCS-based ALE in Ge. The Si dose increases with increasing DCS exposure time. At 500 and 400°C, the Si adsorption proceeds continuously, while at 300°C, the adsorbed Si dose tends to saturate at ~2 monolayers. H-termination of the Ge and Si adsorbed surface suppresses the Si adsorption. Segregated Ge on the adsorbed Si causes further Si adsorption. The adsorbed Si dose is determined by the equilibrium of adsorption/desorption of Si, H and Cl, as well as Ge segregation. By engineering number of Si spikes and Ge spacer thickness as well as following postannealing temperature, uniform low-concentration Si-doped selective Ge layer fabrication is demonstrated which is applicable for operation wavelength tuning of Ge electro-adsorption modulator.
(13) Influence of Strain and Initial Reactions on Epitaxial SiGe Growth
Y. Yamamoto, W.-C. Wen, F. Bärwolf, J. Schlipf, O. Fursenko, S. Karki, M.H. Zoellner, J. Murota, B. Tillack
Materials Science in Semiconductor Processing 209, 110572 (2026)
DOI: 10.1016/j.mssp.2026.110572
Heteroepitaxial growths of SiGe (0 – 40%) on fully relaxed SiGe virtual substrate (VS) with various Ge content (0 – 44%) are investigated to clarify the influence of strain and the initial surface on the SiGe growth. The deposition is performed using H2-SiH4-GeH4 based chemical vapor deposition (CVD) on planarized SiGe substrates, achieved by chemical mechanical polishing (CMP). The CMP interface is separated from the heteroepitaxial interface by depositing a homoepitaxial SiGe buffer layer on the SiGe VS, followed by a top heteroepitaxial SiGe growth. No relaxation of the top SiGe is confirmed for all combinations of the top SiGe and the SiGe buffers. With increasing tensile strain, an increase in the Ge content and a decrease in the growth rate are observed. The increase in the Ge content is more pronounced for the top SiGe growth with higher Ge content. It seems the surface reaction of SiH4 on the SiGe growth front is reduced by higher tensile strain. The top SiGe with higher Ge content shows higher interface pile-up of Ge, and the pile-up is pronounced on the SiGe buffer with higher Ge content as well as higher growth temperature, indicating non-equilibrium reaction at the initial stage of the SiGe growth. These results obtained here enable precise control of heteroepitaxial SiGe growth by CVD.
A. Bhutani, J. Yin, E. Bekker, J. Dittmer, J. Blank, K. Joy, P. Krüger, T. Voß, C. Carta, M. Wietstruck, T. Zwick
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(ESSENCE-6GM)
(2) Ultra-Broadband Photonic Signal-Processor
N. Hanik, T. Kernetzky, U. Höfler, Y. Jia, C. Schubert, M. Karvar, I. Sackey, R. Freund, G. Ronniger, L. Zimmermann
Electronic-Photonic Integrated Systems for Ultrafast Signal Processing, 1st Edition, Editors: J.C. Scheytt, C. Kress, M. Berroth, S. Pachnicke, J. Witzens, Chapter 1. Ultra-Broadband Photonic Signal-Processor, Springer, 1 (2026)
DOI: 10.1007/978-3-032-08340-1_1
(3) Design and Characterization of a Differential UWB LNA Intended for Space Applications
A. Harneer Suresh, G. Fischer, D. Martynenko, F. Korndörfer, C. Carta
Proc. 17th German Microwave Conference (GeMiC 2026), (2026)
(AMX IP)
(4) A Compact Differential DC-203 GHz Variable-Gain Amplifier in a 130-nm SiGe BiCMOS Technology
T. Herbel, C. Heine, M. Wietstruck, D. Kissinger
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(5) Micro-Transfer Printing of SiGe BiCMOS Electronic Chiplets on Silicon
H. Li, T. Pannier, Y. Gu, P. Ramaswamy, R. Loi, P. Heise, M. Inac, A. Farrell, A.J. Trindade, A. Fecioru, K. Dhaenens, T. De Baere, N. Singh, L. Bogaert, S. Qin, B. Pan, J. Zhang, G. Van Steenberge, P. Ossieur, G. Roelkens
IEEE Journal of Selected Topics in Quantum Electronics 32(2), 6000208 (2026)
DOI: 10.1109/JSTQE.2026.3664420
We demonstrate micro-transfer printing (μTP) and post-printing metallization of thin electronic chiplets on silicon, with a view to heterogeneously integrate electronic integrated circuits (EICs) with photonic integrated circuits (PICs). μTP decouples the fabrication of EICs and PICs, and simultaneously enables their tight integration with high-throughput, small form-factor and on wafer-scale. In this study, we successfully established the process flow for releasing and printing 300 μm × 200 μm SiGe BiCMOS electronic driver chiplets and electrically connecting these chiplets using a polymer ramp to overcome the 20-μm chiplet thickness, providing a gain of 14 dB and bandwidth of over 35 GHz with low-parasitic interconnections. The proposed methodology provides a practical and mass-producible solution to realize the stacking of EICs on silicon photonic wafers for emerging applications such as co-packaged optics (CPO).
(6) Electroluminescence and Franz-Keldysh Modulation Observed in Sn/Ge Multi-Quantum Wells
M. Oehme, D. Marian, M. Wanitzek, C. Spieth, D. Schwarz, F. Bärwolf, M.A. Schubert, A. Daus, M. Virgilio, G. Capellini
Advanced Optical Materials 14(9), e03561 (2026)
DOI: 10.1002/adom.202503561, (IHP- Roma Tre University Joint Lab)
Thanks to their tunable electronic and optical properties, GeSn alloys have emerged as promising materials for next-generation silicon-compatible optoelectronic devices operating at extended near- to mid-infrared wavelengths. In this work, we experimentally and theoretically investigate the optoelectronic properties of p-type/intrinsic/n-type (PIN) diodes based on ultrathin α-Sn/Ge multiple quantum well (MQW) structures grown by molecular beam epitaxy with different Ge barrier thicknesses. Thorough structural analysis confirms the high crystalline quality of the MQW and clearly defined interfaces with Sn contents in the wells exceeding 4 at.%. Room-temperature electroluminescence measurements reveal two direct transitions: an MQW stack independent higher-energy emission, related to direct radiative recombination in intrinsic Ge, and a Ge barrier-dependent lower-energy peak, attributed to transitions involving weakly quantum-confined states, whose energy shifts with the barrier thickness in agreement with theoretical prediction. In line with this observation, the devices exhibit clear signatures of the Franz–Keldysh effect when operated as photodetectors, in a wavelength range extending well beyond the direct gap of Ge, as captured by theoretical modeling. These results demonstrate the potential of α-Sn/Ge MQWs as an integrable material platform for complementary metal—oxide–semiconductor (CMOS)-compatible electro-optical modulators spanning the near- to mid-infrared range.
(7) Influence of Illumination Conditions on Photoluminescence Enhancement in an Al/Si/Ge Metasurface
P. Oleynik, D. Ryzhak, J. Schlipf, C.A. Chavarin, Y. Yamamoto, F. Berkmann, M. Ratzke, I.A. Fischer
Optics Express 34(1), 78 (2026)
DOI: 10.1364/OE.577751
Strong field enhancement supported by metasurfaces at resonance can be used to control and enhance the spontaneous emission rate of emitters. This is particularly relevant for emitters with comparatively low quantum yield such as germanium. Here, we investigate the µ-photoluminescence response obtained from a hybrid metasurface comprising a square lattice of Al/Si/Ge pillars. We explore how variations in excitation energy, excitation intensity and number of excited meta-atoms affect the spectral dependence of the photoluminescence signal and, in particular, the contribution of the metasurface to it. Our metasurface exhibits a magnetic dipole collective lattice resonance, whose contribution to the photoluminescence signal increases with increasing number of excited meta-atoms. Measuring only one metasurface under different illumination conditions can potentially be an alternative approach to probe the transition between finite-size effects and collective effects.
(8) X-Ray Characterization of Multilayered SiGe Nanodots Depending on the Si Spacer Growth Temperature
R. Suenaga, Y. Ito, W.-C. Wen, Y. Yamamoto, N. Sawamoto, K. Omote, A. Ogura
Materials Science in Semiconductor Processing 208, 110553 (2026)
DOI: 10.1016/j.mssp.2026.110553
SiGe nanodots (NDs) are attractive materials because of their potential for optoelectronic device applications and their high compatibility with Si-based semiconductor technologies. To develop SiGe NDs as effective optoelectronic devices, it is crucial to characterize the SiGe composition and strain to understand their band structure. In this paper, we present the characterization of SiGe NDs/Si spacer multilayered structures with different Si spacer growth temperatures using lab-based X-ray diffraction (XRD) and reciprocal space mapping (RSM). The RSM determined the spatial arrangement and Ge content of the SiGe NDs. The results showed a decrease in Ge content in the SiGe NDs as the Si spacer growth temperature increased. In-plane XRD measurements revealed the coexistence of tensile- and compressively strained regions within the SiGe NDs and Si spacers, with the proportion of strained regions increasing at higher Si spacer growth temperatures. The calculated bandgap energy of the type-II heterointerface between the Si spacer and SiGe NDs, based on the SiGe composition and strain states determined by XRD and RSM, aligns well with the previously reported blue shift in photoluminescence as the Si spacer growth temperature increased.
(9) A Bidirectional Shunt-Switch D-Band Mixer with a Double-Balanced Combining-Filter in a 130-nm BiCMOS Technology
A. Tiefenbach, L. Zimmermann, D. Kissinger
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(10) Monolithically Integrated Optical Through-Silicon Waveguides for 3D Chip-to-Chip Photonic Interconnects
F. Villasmunta, P. Heise, M. Breiter, S. Schrader, H. Schenk, M. Regehly, A. Mai
IEEE Journal of Selected Topics in Quantum Electronics 32(2), 3700215 (2026)
DOI: 10.1109/JSTQE.2025.3615001
The scaling limitations of electrical interconnects are driving the demand for efficient optical chip-to-chip links. We report the first monolithic integration of air-clad optical through-silicon waveguides in silicon, fabricated via Bosch and cryogenic deep reactive-ion etching. Rib, single-bridge, and double-bridge designs with 50 μm cores and up to 150 μm propagation lengths have been evaluated. Cryogenic-etched rib waveguides achieve the highest median transmission (66%, −1.80 dB), compared to Bosch-etched ribs (62%, −2.08 dB). Across all geometries, 3 dB alignment windows range from 9.3 μm to 49.2 μm, with Bosch-etched double-bridge waveguides providing the broadest tolerance. We show that geometric fidelity outweighs sidewall roughness for transmission and alignment in these large-core, multimode optical through-silicon waveguides. This technology provides a scalable, complementary metal-oxide semiconductor-compatible pathway toward 3D photonic interconnects.
(11) Silicon Interposer with Advanced RF Technology Modules for BiCMOS Wafer-Level Packaging
M. Wietstruck, P. Krüger, T. Voß, S. Schulze, M.F. Bashir, S. Tolunay Wipf, E.C. Durmaz, K. Joy, N. Hasnayen, B. Sütbas
Proc. 17th IEEE German Microwave Conference (GeMiC 2026), (2026)
(ESSENCE-6GM)
(12) Atomic Layer Epitaxy of Si in Ge
Y. Yamamoto, W.-C. Wen, F. Bärwolf, M.A. Schubert:, D. Steckler, J. Murota, B. Tillack
Japanese Journal of Applied Physics 65(1), 01SP02 (2026)
DOI: 10.35848/1347-4065/ae2c94, (Photonics)
Atomic-layer epitaxy (ALE) of Si in Ge using SiH2Cl2 (DCS) is investigated by a cyclic process of selective Ge epitaxy and DCS exposure using chemical vapor deposition. Steep Si profile < 0.6 nm/dec. is realized by the DCS-based ALE in Ge. The Si dose increases with increasing DCS exposure time. At 500 and 400°C, the Si adsorption proceeds continuously, while at 300°C, the adsorbed Si dose tends to saturate at ~2 monolayers. H-termination of the Ge and Si adsorbed surface suppresses the Si adsorption. Segregated Ge on the adsorbed Si causes further Si adsorption. The adsorbed Si dose is determined by the equilibrium of adsorption/desorption of Si, H and Cl, as well as Ge segregation. By engineering number of Si spikes and Ge spacer thickness as well as following postannealing temperature, uniform low-concentration Si-doped selective Ge layer fabrication is demonstrated which is applicable for operation wavelength tuning of Ge electro-adsorption modulator.
(13) Influence of Strain and Initial Reactions on Epitaxial SiGe Growth
Y. Yamamoto, W.-C. Wen, F. Bärwolf, J. Schlipf, O. Fursenko, S. Karki, M.H. Zoellner, J. Murota, B. Tillack
Materials Science in Semiconductor Processing 209, 110572 (2026)
DOI: 10.1016/j.mssp.2026.110572
Heteroepitaxial growths of SiGe (0 – 40%) on fully relaxed SiGe virtual substrate (VS) with various Ge content (0 – 44%) are investigated to clarify the influence of strain and the initial surface on the SiGe growth. The deposition is performed using H2-SiH4-GeH4 based chemical vapor deposition (CVD) on planarized SiGe substrates, achieved by chemical mechanical polishing (CMP). The CMP interface is separated from the heteroepitaxial interface by depositing a homoepitaxial SiGe buffer layer on the SiGe VS, followed by a top heteroepitaxial SiGe growth. No relaxation of the top SiGe is confirmed for all combinations of the top SiGe and the SiGe buffers. With increasing tensile strain, an increase in the Ge content and a decrease in the growth rate are observed. The increase in the Ge content is more pronounced for the top SiGe growth with higher Ge content. It seems the surface reaction of SiH4 on the SiGe growth front is reduced by higher tensile strain. The top SiGe with higher Ge content shows higher interface pile-up of Ge, and the pile-up is pronounced on the SiGe buffer with higher Ge content as well as higher growth temperature, indicating non-equilibrium reaction at the initial stage of the SiGe growth. These results obtained here enable precise control of heteroepitaxial SiGe growth by CVD.
