A Cryogenic Backward Diode

Abstract

This paper presents results from experiments with a cryogenic diode we developed which can rectify voltage swings from a few millivolts to a few tens of millivolts. The diode consists of an n-type semiconductor with a high dielectric constant, a metal layer, and an intervening tunneling barrier. As the semiconductor, we chose n-SrTiO3, which has a dielectric constant of 2x104 at around 4.2 K. The tunneling barrier was 6-nm-thick Si, the metal electrode 240-nm-thick Nb, and the SrTiO3 carrier concentration 5x1017 cm−3. The diode could rectify a voltage swing of a few tens of millivolts. Curvature coefficient γ (=(d2I/dV2)/(dI/dV)), a measure of nonlinearity, was 380 to 170 V−1 for a bias range of 2 to 10 mV.