Method of detecting electromagnetic radiation with bandgap engineered active pixel cell design

摘要

A method of detecting electromagnetic radiation with an active pixel sensor photosensitive device having an extremely thin virtual pinning layer formed by inverting semiconductor material at the surface of a photosensitive region. The thin pinning layer improves blue light response. The inverted pinning layer is produced by connecting a negative potential source to a transparent conductive layer, preferably made of indium-tin-oxide positioned over most of the photosensitive region. The conductive layer is insulated from the photosensitive region by a thin insulating layer. Connection to the pinning layer is through a coupling region formed in an area not covered by the conductive and insulating layers. Red light response is improved and the depth of the photosensitive region reduced by creating a strained layer, preferably of germanium silicon, deep within the photosensitive region. The strained layer has a modified bandgap which increases the absorption rate of red light.