Abstract
An ac surface photovoltage (SPV) is investigated in the thermally-grown silicon (Si) wafers, which are pretreated with an iron (Fe)-contaminated alkaline solution composed of ammonia hydroxide, hydrogen peroxide, and water. The ac SPV appeared in the cleaned and oxidized p-type Si is reduced by the incorporation of Fe into the thermal oxide, which causes the ac SPV being on the rise in n-type Si, depending on Fe concentration. These results prove that a negative charge due to Fe incorporated in the native oxide survives in the thermal oxide.