Charge-transfer noise theory for surface-channel charge-coupled devices

The detailed expression of charge-transfer noise for surface-channel CCD's is derived from the surface generation-recombination rate equation. Not only the charge fluctuation due to occupied interface states but also that due to unoccupied interface states are taken into account. The derived expression can explicitly predict the spectrum intensity dependences on the signal charge concentration and the clock frequency for various amounts of the fat-zero charge. The comparison between theory and experimental results shows good agreement over a wide range of signal charge concentration and clock frequency. It is shown that charge-transfer noise depends heavily on the ratio of the signal charge concentration to the clock frequency and the capture cross section in the absence of fat-zero charge. For the small ratio, the charge fluctuation is ruled by the transfer-process noise which is determined from the amount of unoccupied interface states. For the very large ratio, the storage-process noise which is determined from the interface state distribution over the band gap rules the charge fluctuation. Fat-zero charge hardly reduces the transfer-process noise for the small ratio. For the large ratio, the fat-zero charge enhances the total transfer noise.