Amir Sammak, Diego Sabbagh, Nico W. Hendrickx, Mario Lodari, Brian Paquelet Wuetz, Alberto Tosato, LaReine Yeoh, Monica Bollani, Michele Virgilio, Markus Andreas Schubert, Peter Zaumseil, Giovanni Capellini, Menno Veldhorst, Giordano Scappucci, Sammak, Amir, Sabbagh, Diego, Hendrickx, Nico W., Lodari, Mario, Paquelet Wuetz, Brian, Tosato, Alberto, Yeoh, Lareine, Bollani, Monica, Virgilio, Michele, Schubert, Markus Andrea, Zaumseil, Peter, Capellini, Giovanni, Veldhorst, Menno, and Scappucci, Giordano
Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 105 cm2 V−1 s−1) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 1011cm−2, light effective mass (0.09me), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.