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 10¹⁸ ～ 10²⁰ 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 10¹⁹ ～ 10²⁰ cm^?3 eV^?1 and native defect states of about 10¹⁸ cm^?3 eV^?1.