Charger transfer device (CTD), eliminating the background level of a detected signal, detection structure and method of using such a CTD

Claim 1

A charge transfer device for reading out a radiation detector, comprising means for eliminating the background level of the radiation to be detected, and comprising an input circuit and a transfer circuit, formed in a semiconductor substrate, said input circuit comprising: a charge injection source connected to said detector, which supplies a quantity of charge; a storage electrode for forming a storage potential well in the semiconductor substrate in which electric charge injected by the source can be stored; a control electrode between the source and the storage electrode, which permits injection of charge from the source into the storage potential well; a separation electrode, isolated from the storage electrode for subdividing said storage well into an evacuation well and an output well separated from each other by a separation potential formed by said separation electrode, which permits retention in the evacuation well of a quality of charge to be evacuated and retention in the output well a quantity representative of the useful signal which is read by the transfer circuit, while the charge in the evacuation well can be evacuated by means of a reset transistor; a floating electrode connected to the separation electrode for controlling the potential of the separation electrode, said potential of the separation electrode being determined during a calibration operation, said floating electrode being located besides the separation electrode, the doping under the floating electrode and the separation electrode being different from each other and such that potential wells under these electrodes have different depths; and and insulation electrode disposed between the separation electrode and the floating electrode, by means of which the well under the floating electrode and the output well can be separated from each other.