Transverse gate electric field

Since extrinsic silicon photoconductor material has high resistivity at cryogenic temperatures it can be used to form the substrate of an accumulation mode CCD as shown in Fig. 6.11. With an accumulation mode MIS structure the gates are biased so that majority carriers are stored and transferred down the insulator semiconductor interface. Local potential wells are formed under the gates however the dynamics of the charge transfer process will be very different from those for an inversion mode device since with an accumulation mode device the transverse electric fields will extend all the way to the back contact instead of being confined to the depletion region of an inversion mode structure. 

Fig. 5.2-70 Effective mobility of electrons and holes in MOSFET s inversion channel. Qs = gtotai is the charge on the gate electrode. It is seen that mobility decreases at high transverse electric fields. For comparison, bulk mobilities are fin — 1600, fip = 600cm- /V s [2.96]...

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