Ge/SiGe 2DHG Transistors for Cryogenic Electronics
Strained Germanium (Ge) quantum wells (QWs) have emerged as one of the promising material platforms for the next generation of cryogenic and quantum electronics. Epitaxially grown Ge on SiGe heterostructures offers ultra-high hole mobility exceeding 1 x 105 cm2/Vs at temperature below 10 K. By utilizing biaxial compressive strain, we lift valence band degeneracy and significantly reduce the effective mass of holes, enhancing carrier velocity and reducing scattering [1]. Furthermore, undoped Ge/SiGe heterostructures allow for a significant reduction in charge noise and parasitic channel effects, making the platform better suited for the sensitive manipulation of quantum dots near quantum hardware.
The Ge/SiGe two-dimensional hole gas (2DHG) platform is a leading candidate for quantum computing readout and control. Holes in Ge exhibit strong spin-orbit interaction, enabling fast electrical manipulation of spin qubits, while a weak hyperfine interaction ensures longer coherence times compared to other semiconductor systems. Moreover, Ge QWs offer superior integration with Si-based CMOS workflows unlike III-V platforms.
This project aims to develop Ge/SiGe 2DHG transistors for cryogenic electronics. The project includes:
Design: Optimize device geometries to control gate coupling and electrostatic screening in the low-dimensional regime.
Fabrication: Develop new cleanroom processes (lithography, etching, and deposition) in PSI cleanroom.
Characterization: Perform cryogenic electrical measurements.
We are looking for a highly motivated student with a strong background in semiconductor physics or electronics. In addition, you will be hands-on in developing fabrication; therefore, a strong interest or prior experience in nanofabrication is preferred.
Please note that we cannot provide visa support for this position. Additionally, no financial compensation or stipend is offered.
Please contact us to learn more about the opportunity: eunjung.cha@psi.ch
[1] A. Nigro et al., “Strain Engineering of Ge Quantum Wells in Planar Ge/Si1 − xGex Heterostructures,” Advanced Materials Interfaces, vol. 12, no. 24, p. e00620, Dec. 2025, doi: 10.1002/admi.202500620.
