Breakdown of Al/AlOx/Al Tunneling Junctions

概要

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The breakdown of Al/AlOx/Al tunneling junctions is studied. Al (10 nm)/AlOx(${\sim}2.5$ nm)/Al (50 nm) tunneling junctions were fabricated on glass substrates by ion-beam mask sputtering. The sputtered Al film was oxidized in pure O2 gas for 4–40 h at room temperature. The AlOx barrier height evaluated from a fit to the Simmons-Schottky equation was 0.38–1.7 eV. The current-voltage characteristics were measured by the four-probe method. The breakdown of Al/AlOx/Al tunneling junctions can be classified into two types on the basis of current-voltage characteristics. Type 1 breakdown shows an abrupt increase in current and a decrease in resistance at the maximum applied voltage. This type of breakdown occurs at the voltage when the energy level of the AlOx valence band is equal to the barrier height. It is concluded that type 1 breakdown is caused by the Zener mechanism. Type 2 breakdown shows an erratic change of current and resistance. The average electrical resistivities of AlOx are $7.8{\times}10^{3}$ and $1.1{\times}10^{3}$ $\Omega$m for specimens showing type 1 and type 2 breakdowns, respectively. It is considered that some defects in AlOx result in the low breakdown voltage for type 2 breakdown.
2004-01-15