Andreas Mai

Conventional Si Complementary Metal Oxide Semiconductor (CMOS) technologies face increasing challenges in improving energy efficiency while maintaining device performance. Here, SiGeSn/GeSn heterostructures are employed as a unified Group‐IV platform for complementary vertical nanowire gate‐all‐around (GAA) MOSFETs and tunnel field‐effect transistors (TFETs) fabricated on Si wafers. The wider‐bandgap SiGeSn source/drain regions introduce band offsets to the GeSn channel, enabling heterostructure band engineering for leakage suppression and tunneling‐pathway control. Compared with all‐GeSn reference devices, the SiGeSn source/drain architecture suppresses drain‐induced barrier lowering and off‐state leakage without modifying the GeSn channel. The same heterostructure platform also enables complementary TFET operation, where the n‐TFET exhibits a subthreshold swing of 60 mV dec ^{− 1} and a two‐order‐of‐magnitude enhancement in on/off current ratio. The performance difference between p‐ and n‐TFETs provides experimental evidence of the different efficiencies of indirect Γ‐to‐L and direct Γ‐to‐Γ tunneling processes. These results demonstrate that SiGeSn/GeSn heterostructures can be used to suppress leakage currents and engineer tunneling pathways, establishing SiGeSn/GeSn heterostructures as a unified Group‐IV platform for future energy‐efficient CMOS technologies beyond conventional Si.

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.

Si-based photonics has garnered considerable attention as a future device for complementary metal–oxide–semiconductor (CMOS) computing. However, few studies have investigated Si-based light sources highly compatible with Si ultra large-scale integration processing. In this study, we observed stable light emission at room temperature from superatom-like β–FeSi₂–core/Si–shell quantum dots (QDs). The β–FeSi₂–core/Si–shell QDs, with an areal density as high as ~10¹¹ cm⁻² were fabricated by self-aligned silicide process of Fe–silicide capped Si–QDs on ~3.0 nm SiO₂/n–Si (100) substrates, followed by SiH₄ exposure at 400 °C. From the room temperature photoluminescence characteristics, β–FeSi₂ core/Si–shell QDs can be regarded as active elements in optical applications because they offer the advantages of photonic signal processing capabilities and can be combined with electronic logic control and data storage.

Photonic integrated circuits (PIC) are like electronic integrated circuits drivers of communication systems. Moreover, state-of-the-art technologies enable the fabrication of electronic-photonic integrated circuits (ePIC), which allows for example the cointegration of ultra-fast BiCMOS devices with high speed photo detectors. Besides that, this technology provides an attractive platform for biosensors. They open the door for label-free detection of various analytes with high specificity and in real-time. This gives perspective to highly scalable and cost effective technologies for smart system integration of biosensors and electronic readouts to realize a true lab-on-a-chip application. We present the integration of optical biosensors in a Si-based PIC-technology. This comprises a front-end of line with optical waveguides, an integrated Ge-photodiode and a complete back-end of line consisting of three thin and two thick aluminum metal layers. The optical biosensor is integrated by opening the optical waveguide from the backside of the chip. In particular, we released a Si-based slot waveguide, which provides an enhanced evanescent field to interact with the analyte and hence to increase the sensitivity. The slot waveguide is incorporated in a ring resonator and we analyzed the wafer-level performance using the full width at half maximum, which allows us to assess the optical losses. Thermal sensing in a wide temperature range is investigated. In addition, a simple and cost-effective microfluidic is realized and we show initial results of the surface functionalization. Our work demonstrates the compatibility of a photonic biosensor with a photonic integrated circuit technology without any restriction to the standard FEOL and BEOL processing on the wafer front-side, while it keeps the inherent high sensitivity of evanescent-field sensing and opens a route towards smart system integration. Figure 1

2023 International Conference on Solid State Devices and Materials ,Vertical Gate-All-Around SiGeSn/GeSn/SiGeSn Nanowire nFETs

This invited paper reviews the progress of silicon-based integrated analyzers for biomedical applications over the last two decades. Focus is set on various integrated circuit realizations in the millimeter-wave range from 30 GHz and at the terahertz frequencies of above 300 GHz. This article discusses high-frequency architectures and concrete implementations of both narrowband as well as broadband integrated readout circuits, including their use in miniaturized sensor solutions. A variety of circuits ranging from low-power sensing oscillators to highly integrated broadband vector network analyzers (VNAs), and example realizations of millimeter-wave cardiovascular sensors and implants to THz microfluidic labs-on-chip and exhaled human breath analyzers are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of such biomedical sensors toward reliable and specific systems.