Reduction of defects in laser-induced crystallized and amorphized silicon films using plasma hydrogenation

Abstract

Plasma hydrogenation of laser-crystallized and -amorphized films was investigated. The hydrogen concentration was determined to be 1.5 at. % using a method of laser-induced hydrogen effusion for 20-nm-thick crystallized films which were hydrogenated at 250 °C for 30 s. The defect density was reduced from 1×1017 to 4×1016 cm−3. The hydrogen concentration was 2.5 at. % for amorphized films of 12 nm-thickness. This low hydrogen concentration resulted in a low optical band-gap energy of 1.7 eV for amorphized films, while the width of the Urbach tail was 0.06±0.005 eV, which is close to that of hydrogenated amorphous silicon (a-Si:H) films fabricated using radio-frequency glow discharge (rf GD). The defect density of the laser-amorphized silicon films was reduced from 2×1020 to 4×1015 cm−3 eV−1 comparable to a-Si:H films fabricated by rf GD.