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

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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.