Electric-field-enhanced crystallization of amorphous silicon

Abstract

Thin films of polycrystalline silicon are of great importance for large-area electronic applications, providing, for example, the switching electronics in many flat-panel displays. Polycrystalline silicon is typically produced by annealing films of amorphous silicon¹ that have been deposited from the vapour phase, and much research is focused on lowering the crystallization temperature. It is known that the solid-phase crystallization temperature of amorphous silicon can be reduced by the addition of certain metals², such as nickel³. Here we show that the rate at which this metal-induced crystallization takes place is markedly enhanced in the presence of an electric field. For example, the crystallization time at 500 °C decreases from 25 hours to 10 minutes on application of a modest (80 V cm⁻¹) electric field. No residual amorphous phase can be detected in the films. A thin-film transistor fabricated from such a film exhibits a field-effect mobility of 58 cm² V⁻¹ s⁻¹, thereby demonstrating the practical utility of these materials.