Recrystallized Al-nSi Schottky barriers with a barrier height of 0.93 eV

Abstract

Using a silicon-aluminum-silicon sandwich structure obtained by evaporating thin aluminum and silicon films on a single-crystal silicon substrate, we have fabricated Al-nSi Schottky barriers with a maximum barrier height of 0.93 eV. The formation of the rectifying contact and its dependence on the Al-film thickness were studied by means of I-V and C-V measurements. It is found that the as-deposited films form an Ohmic contact with a n/n+ silicon substrate. However, we have obtained rectification characteristics by heat treatment at 600 °C (slightly above the Al-Si eutectic temperature) in a nitrogen or hydrogen environment. The barrier height increases with aluminum thickness (l) from 0.79 eV for l=500 Å and it saturates at 0.93 eV for l≳1500 Å. The uppermost silicon film (300 Å) is needed to prevent the formation of aluminum clusters under heat treatment. In completed diodes the surface silicon film is recrystallized and large polycrystalline-Si grains are seen under an optical microscope.