Electron Multiplying Charge-Coupled Devices (EMCCDs)

By incorporating on-chip multiplication gain, the electron multiplying CCD achieves, in an all solid-state sensor, the single-photon detection sensitivity typical of intensified or electron-bombarded CCDs at much lower cost and without compromising the quantum efficiency and resolution characteristics of the conventional CCD structure.

This interactive tutorial illustrates the principle of signal multiplication in the charge multiplication register of an electron multiplying CCD. When a signal electron charge is transferred from stage to stage, the signal charge is accelerated through a high electric field generated under the multiplication gate by applying a high voltage (30 to 40 volts) to each multiplication electrode (multiplication gate). This high voltage is much greater than the normal horizontal transfer electrode voltage, and it generates an occasional extra electron-hole pair. This effect is called an impact ionization event. The probability of such an event is very small, typically about 1.0 to 1.6 percent at each stage. Electrons are multiplied from stage to stage repeatedly in the gain register and high multiplication gain is achieved. Normally, there are 400 to 600 stages in the gain register.