Granular superconductor contacts to two-dimensional electron gases

Superconducting contacts are made to a buried two-dimensional electron gas using metal multilayers (Sn:Cr:Au) patterned by electron-beam lithography, and sintered using rapid electron-beam annealing. The contact structure has been analyzed using transmission electron microscopy and high-resolution scanning electron microscopy, and many alloys are found to be present, but the structure is predominantly a honeycomb mixture of AuSn4 and CrAs. The resultant contacts are granular superconductors with relatively high critical temperatures of 5-7.5 K. (C) 1996 American Vacuum Society.