Hybrid superinductance with Al/InAs

We report microwave spectroscopy of Josephson junctions chains made from an epitaxial Al/InAs heterostructure. The chains exhibit superinductance, with characteristic wave impedance exceeding $R_Q=\mathrm{\hslash }\mathrm{/}(2e{)}^2$. The planar nature of the junctions results in a large plasma frequency, with no measurable deviations from ideal dispersion up to $12\mathrm{G}\mathrm{H}\mathrm{z}$. Internal quality factors decrease sharply with frequency, which we describe with a simple loss model. The possibility of a loss mechanism intrinsic to the superconductor-semiconductor junction is considered.