Molecular beam epitaxy growth of superconducting tantalum germanide

Abstract

Developing new material platforms for use in superconductor-semiconductor hybrid structures is desirable due to limitations caused by intrinsic microwave losses present in commonly used III/V material systems. With the recent reports on tantalum superconducting qubits that show improvements over the Nb and Al counterparts, exploring Ta as an alternative superconductor in hybrid material systems is promising. Here, we study the growth of Ta on semiconducting Ge (001) substrates grown via molecular beam epitaxy. We show that at a growth temperature of 400${}^{\circ }$C the Ta diffuses into the Ge matrix in a self-limiting nature resulting in smooth and abrupt surfaces and interfaces with roughness on the order of 3-7 Å as measured by atomic force microscopy and x-ray reflectivity. The films are found to be a mixture of Ta${}_5$Ge${}_3$ and TaGe${}_2$ binary alloys and form a native oxide that seems to form a sharp interface with the underlying film. These films are superconducting with a $T_C\sim 1.8-2$K and $H_C^{\perp }\sim 1.88T$, $H_C^{\parallel }\sim 5.1T$. These results show this tantalum germanide film to be promising for future superconducting quantum information platforms.

References in corpus (7)

• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Hard superconducting gap in germanium
• Chemical profiles of the oxides on tantalum in state of the art superconducting circuits
• Lightly-strained germanium quantum wells with hole mobility exceeding one million
• Superconducting resonators with voltage-controlled frequency and nonlinearity
• Electrical operation of planar Ge hole spin qubits in an in-plane magnetic field
• Investigating microwave loss of SiGe using superconducting transmon qubits

Cited by in corpus (5)

• Progress in superconductor-semiconductor topological Josephson junctions
• Germanium-based hybrid semiconductor-superconductor topological quantum computing platforms: Disorder effects
• Dephasing of planar Ge hole spin qubits due to 1/$\text{f}$ charge noise
• Superconductivity in Substitutional Ga-Hyperdoped Ge Epitaxial Thin Films
• Heat-charge separation in a hybrid superconducting quantum Hall setup