Effects of various hydrogen-passivation techniques on the performance of a-SiC:H-based p-i-n-type thin-film visible-light-emitting diodes

Abstract

The effects of various hydrogen-passivation processes on the performance of a-SiC:H-based p-i-n-type thin-film visible-light-emitting diodes (TFLEDs) fabricated by a photo-CVD method have been investigated. A hydrogen-passivation process was performed by three methods: in-situ hydrogen passivation by a photo-CVD method, ex-situ hydrogen passivation via a plasma, and two-step hydrogen passivation in which the in-situ hydrogen-passivation process was followed by an ex-situ one. It was found that a hydrogen-passivation process remarkably improved the device performance and that the two-step hydrogen-passivation process was most effective; i.e., decrease of the threshold voltage by about 2 V, shift of the EL peak wavelength from 700 to 590 nm, and increase of the luminance up to 128 cd/m2; and that improvement of the device performance by the hydrogen-passivation process was dominantly caused by a decrease of midgap states by hydrogen atoms.