Current in Plane Tunneling for Josephson Junction development

Josephson junctions play a pivotal role in constructing superconducting qubits, featuring a layered structure of superconductor-insulator-superconductor. They consist of a layered structure formed by a superconductor-insulator-superconductor. The resistance of the junctions determines the frequency at which the qubit operates, therefore, it is crucial to have control over the parameters that determine this value. The resistance of a junction is determined by its area and by its RnA product. This parameter depends on the thickness of the barrier, the insulator used as a barrier and even in the roughness of the layer underneath the insulator.

Traditionally, RnA is established by crafting junctions with varying areas and gauging their normal resistance, but this proves to be a time-consuming endeavor. The fabrication of Josephson junctions necessitates two stages of ebeam lithography and extended hours of device measurements. An alternative method for ascertaining the RnA value is Current in Plane Tunneling (CIPT). This approach enables the determination of RnA within a blanket trilayer configuration (superconductor-insulator-superconductor) without the need of any patterning, significantly accelerating the turnaround time for Josephson junction development. Although CIPT has found widespread application in MRAM development, its incorporation into the realm of quantum computing is relatively recent.

This project aims to fabricate and characterize Al-AlOx-Al trilayers using Current in Plane Tunneling, with the intention of subsequently incorporating them into the production of superconducting qubits. Various trilayers, subjected to different oxidation conditions, will be deposited through ebeam evaporation and thermal oxidation, followed by CIPT characterization. Additionally, the trilayers will undergo annealing to replicate the Josephson junction fabrication process, allowing for an examination of changes in RnA. Subsequently, arrays of Josephson junctions will be fabricated using the developed trilayers, and their RnA values will be compared with those obtained during the initial blanket development. This project aims to establish CIPT as a reliable predictor of Josephson junction normal resistance and introduce this technique for the development of superconducting qubits.