Patent ID: 7217982
Filing Date: 2007-05-15
Classification: H01L

Abstract:
1. A photodetector, comprising: a substrate having a surface; a first layer comprised of semiconductor material that is disposed above said surface, said first layer comprising a first dopant at a first concentration for having a first type of electrical conductivity; and a second layer comprised of semiconductor material overlying said first layer, said second layer comprising a second dopant at a second concentration for having a second type of electrical conductivity and forming a first p-n junction with said first layer, said second layer being compositionally graded through at least a portion of a thickness thereof from wider bandgap semiconductor material to narrower bandgap in a direction away from said p-n junction, where said first concentration is at least an order of magnitude greater than said second concentration, and where when said first p-n junction is reverse biased, a depletion region exists substantially only within said second layer.