Experimental observation of avalanche multiplication in charge-coupled devices

Avalanche multiplication of signal charge in surface-channel charge-coupled devices is reported in this paper. Experimental observations show 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, the gain in charge is about 3-percent per transfer. A simple model is developed which explains the experimental data reasonably well. The upper limit to the amplitude of clock voltages that can be applied to a CCD is likely to be determined by this avalanche multiplication mechanism rather than the oxide breakdown criterion.