Characterization of superconductivity in doped Ga:Ge thin films grown by molecular beam epitaxy

Germanium (Ge) has emerged as a promising candidate for housing quantum computing architectures through superconducting qubits [1]. As a group IV semiconductor, it has been shown to undergo a metal-insulator transition when doped with gallium (Ga) [2] and at high enough concentrations attainable by ion implantation, superconductivity is observed [3]. In particular, we examine this phenomenon when the films are grown through molecular beam epitaxy (MBE). We measure an increase in T_C from 0.8K-2K and B_C from 50mT to 250mT suggestive of strong confinement effects. Enhanced in-plane B_C up to 1.3T is observed and will be discussed in the context of Ginzburg-Landau theory. Finally, future use in quantum information circuitry will be briefly discussed.

[1] Scappucci, Giordano, et al. "The germanium quantum information route." Nature Reviews Materials 6.10 (2021): 926-943.

[2] Persson, Clas, A. Ferreira da Silva, and Börje Johansson. "Metal-nonmetal transition in p-type SiC polytypes." Physical Review B 63.20 (2001): 205119.

[3] Sardashti, Kasra, et al. "Tuning superconductivity in Ge: Ga using Ga+ implantation energy." Physical Review Materials 5.6 (2021): 064802.