Abstract
Hybrid superconductor-semiconductor materials systems are promising candidates for quantum computing applications. Their integration into superconducting electronics has enabled on-demand voltage tunability at millikelvin temperatures. Ge quantum wells have been among the semiconducting platforms interfaced with superconducting Al to realize voltage tunable Josephson junctions. Here, we explore Nb as a superconducting material in direct contact with Ge channels by focusing on the solid-state reactions at the Nb/Ge interfaces. We employ Nb evaporation at cryogenic temperatures (∼100 K) to establish a baseline structure with atomically and chemically abrupt Nb/Ge interfaces. By conducting systematic photoelectron spectroscopy and transport measurements on Nb/Ge samples across varying annealing temperatures, we elucidated the influence of Ge out-diffusion on the ultimate performance of superconducting electronics. This study underlines the need for low-temperature growth to minimize chemical intermixing and band bending at the Nb/Ge interfaces.
| Original language | English |
|---|---|
| Article number | 095311 |
| Journal | AIP Advances |
| Volume | 14 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 1 2024 |
Funding
This work was supported by the National Science Foundation (Award No. 2137776) and the U.S. Department of Energy (Award No. DE-SC0023595). Fabrication of niobium microwires was conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. RBS measurements were performed at the Laboratory of Surface Modifications at Rutgers University. B.L. and K.S. acknowledge Kelliann Koehler and the Clemson Electron Microscopy Facility for their assistance conducting the XPS measurements. M.K. was partly supported by the Louis Beecherl, Jr. Endowed Fund.