The Buried Channel Charge Coupled Device

摘要: The charge-coupled device, as described originally by Boyle and Smith,1 operates moving minority carriers along the surface of a semiconductor with voltage pulses applied to metal electrodes which are separated from an insulating layer. transit one electrode next is determined carrier transport under influence their own potential, fringing fields, diffusion, trapping properties interface states. limitations largely device geometry;2 for 10-μm electrodes, thermal diffusion predominantly responsible transferring last small amounts charge forward limits efficient operation clock frequencies below 10 MHz. Surface state much less dispersive, even at low 1011 states/cm2 eV can impose requirement regeneration after few 100 transfers.3,4 In order circumvent these problems, Smith5 have proposed modified CCD structure in charges do not flow surface; instead they confined channel lies beneath surface. This buried has potential eliminating trapping. (Bulk should be several orders magnitude important loss mechanism.) Calculations show that this modification will give rise increased fields electrodes. Diffusion replaced factor intrinsic transfer process more powerful field-aided transfer. leads fast, when very little remains transferred. addition advantages, higher mobility found bulk further enhance speed device.2