Fig. 14.

Schematic of MAPS CMOS detector. The pixel spacing is determined by the spacing between diodes formed by the $\mathrm{N}$ well doped areas indicated in blue. The division into three layers used in the simulations is indicated and consists of: (a) passivation and heavily doped wells; (b) sensitive layer consisting of the lightly doped epilayer; and (c) heavily doped substrate. The track of an incident electrons is shown illustrating the problem with backscattering from the substrate in a non-backthinned detector. The diffusive collection by the reverse biased $\mathrm{N}$ well diodes of mobile electrons generated in electron-hole pair excitations is indicated.