Measurements of localized-state density in chemically vapour deposited amorphous silicon by the field-effect method

New techniques to determined the localized-state density in chemically vapour deposited amorphous silicon over a wide energy range by the field-effect method are presented. The density is measured for the first time as 10 18 ∼ 10 20 cm −3 eV −1 in the range ±0.4∼±0.5 eV around the Fermi level. From the results it is suggested that the silicon atom network of CVD a-Si has a similar randomness to that of glow discharge a-Si, providing a density of tail states of about 10 19 ∼ 10 20 cm −3 eV −1 and native defect states of about 10 18 cm −3 eV −1 .