Patent ID: 8044476

Claim:
A radiation detector, comprising: a CdTe or CdZnTe compound semiconductor substrate that absorbs X-radiation having a first energy and has a main surface and a rear surface opposite to each other through the CdTe or CdZnTe compound semiconductor substrate; a CdTe or CdZnTe compound semiconductor layer of a first conductivity type having first and second surfaces opposite to each other through the CdTe or CdZnTe compound semiconductor layer, and the first surface of the CdTe or CdZnTe compound semiconductor layer being attached to the main surface of the CdTe or CdZnTe compound semiconductor substrate; a metal layer consisting essentially of metallic In and having first and second surfaces opposite to each other through the metal layer, wherein the first and second surfaces of the metal layer do not meet each other, the first surface of the metal layer being attached to the second surface of the CdTe or CdZnTe compound semiconductor layer; a Si semiconductor layer of a second conductivity type opposite to the first conductivity type, having first and second surfaces opposite to each other through the Si semiconductor layer, and the first surface of the Si semiconductor layer being attached to the second surface of the metal layer; and a Si semiconductor substrate that absorbs X-radiation having a second energy different from the first energy and has first and second surfaces opposite to each other through the Si semiconductor substrate, the first surface of the Si semiconductor substrate being attached to the second surface of the Si semiconductor layer.