Ohmic, superconducting, shallow AuGe/Nb contacts to gaas

M. Gurvitch, A. Kastalsky, S. Schwarz, D. M. Hwang, D. Butherus, S. Pearton, C. R. Gardner

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

An emerging new class of superconductor-semiconductor devices requires Ohmic superconducting contacts which do not diffuse deeply into a semiconductor. We developed a contact to GaAs based on ∼150 Å of AuGe covered with ∼2000 Å of Nb annealed in reducing atmosphere at 390-420 °C for 1-5 s. The resulting contact has linear I-V characteristics at all temperatures down to 4.2 K, resistivity of ∼2×10-6 ω cm2 (∼0.1 ω mm), and superconducting transition temperature Tc ≳8 K. Secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM) studies revealed very shallow penetration of the active dopant Ge into GaAs; the upper limit for the thickness of the doped layer with Ge concentration over 1017 cm -3 is estimated as 200-300 Å. Gold, a nonactive dopant (deep level) drops to below 1018 cm -3 within the same distance, with the possible tail extending further. Morphology and uniformity of a contact, as revealed in TEM and optical microscopy, is good, owing to the Nb overlayer which prevents AuGe from "balling up" upon melting. These contacts can be used in low-temperature devices and conventional devices based on GaAs.

Original languageEnglish (US)
Pages (from-to)3204-3210
Number of pages7
JournalJournal of Applied Physics
Volume60
Issue number9
DOIs
StatePublished - 1986
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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