Richard Crisp published his paper about Residual Bulk Image (RBI) in CCDs on his web site. The paper was presented at recent IS&T/SPIE's Electronic Imaging Symposium, San Jose Ca. January 21, 2009. One needs to click on picture to download the pdf file.
While I don't entirely agree with Richard's explanations, the RBI phenomenon itself is quite interesting and the paper is certainly worth reading. By the way, Richard's site has a lot of other imaging-related information.
Update: Richard Crisp adds a bit of explanation to my post:
... my intent behind the paper was to really focus on the characterization and management of RBI, not so much to explain the phenomenon. That has been done many times by others. Janesick discusses it in detail in his book on Scientific CCDs. I only wanted to lightly touch on the root cause and then discuss how to quantify it and to assess the impact of its management on noise of ccds.