TY - JOUR
T1 - Hard Superconducting Gap and Diffusion-Induced Superconductors in Ge–Si Nanowires
AU - Ridderbos, Joost
AU - Brauns, Matthias
AU - de Vries, Folkert K.
AU - Shen, Jie
AU - Li, Ang
AU - Kölling, Sebastian
AU - Verheijen, Marcel A.
AU - Brinkman, Alexander
AU - van der Wiel, Wilfred G.
AU - Bakkers, Erik P.A.M.
AU - Zwanenburg, Floris A.
N1 - ACS deal
PY - 2020/1/8
Y1 - 2020/1/8
N2 - We show a hard superconducting gap in a Ge–Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9–1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.
AB - We show a hard superconducting gap in a Ge–Si nanowire Josephson transistor up to in-plane magnetic fields of 250 mT, an important step toward creating and detecting Majorana zero modes in this system. A hard gap requires a highly homogeneous tunneling heterointerface between the superconducting contacts and the semiconducting nanowire. This is realized by annealing devices at 180 °C during which aluminum interdiffuses and replaces the germanium in a section of the nanowire. Next to Al, we find a superconductor with lower critical temperature (TC = 0.9 K) and a higher critical field (BC = 0.9–1.2 T). We can therefore selectively switch either superconductor to the normal state by tuning the temperature and the magnetic field and observe that the additional superconductor induces a proximity supercurrent in the semiconducting part of the nanowire even when the Al is in the normal state. In another device where the diffusion of Al rendered the nanowire completely metallic, a superconductor with a much higher critical temperature (TC = 2.9 K) and critical field (BC = 3.4 T) is found. The small size of these diffusion-induced superconductors inside nanowires may be of special interest for applications requiring high magnetic fields in arbitrary direction.
KW - UT-Hybrid-D
KW - Superconductor−semiconductor hybrid device
U2 - 10.1021/acs.nanolett.9b03438
DO - 10.1021/acs.nanolett.9b03438
M3 - Article
SN - 1530-6984
VL - 20
SP - 122
EP - 130
JO - Nano letters
JF - Nano letters
IS - 1
ER -