Patent ID: 7858945

Claim:
An imaging detector for detecting ionizing radiation, such as X-rays or electrons, in a predetermined energy range, comprising: a read-out chip including read-out circuitry; and a sensor for absorbing ionizing radiation over a plurality of pixels, the sensor being electrically connected to the read-out chip; wherein the read-out chip has circuitry to record a pulse in a pixel when it detects a charge excited by a photon or electron greater than a threshold charge; and the sensor includes a plurality of sensor material layers of different materials stacked on top of one another, having differing radiation absorbing properties, wherein the plurality of sensor material layers absorbs at least 70% of incident radiation across the predetermined energy range; wherein the sensor material layers include a first sensor material layer of a first semiconductor, a second sensor material layer of a second semiconductor and a buffer layer between the first sensor material layer and the second sensor material layer, wherein the buffer layer has a graded composition varying from the material of the first sensor material layer to the material of the second sensor material layer.