Experimental observation of avalanche multiplication in charge-coupled devices

Observations are presented of the avalanche multiplication of signal charge in surface-channel charge-coupled devices. It is determined that avalanche multiplication takes place when the electrons are made to fall down a steep barrier of more than 8 V in an overlapping gate structure. For a 16 V fall, for example, the gain in charge is found to be about 3 percent per transfer. A simple model is presented which explains the experimental data reasonably well. It is suggested that the upper limit to the amplitude of clock voltages that can be applied to a charge-coupled device will be determined by this avalanche multiplication mechanism rather than the oxide breakdown criterion.