On drift fields in CMOS monolithic active pixel sensors

CMOS Monolithic Active Pixel Sensors (MAPS) combine an excellent spatial resolution of few μm with a very low material budget of 0.05% X₀. To extend their radiation tolerance to the level needed for future experiments like e.g. CBM, it is regularly considered to deplete their active volume. We discuss the limits of this strategy accounting for the specific features of the sensing elements of MAPS. Moreover, we introduce an alternative approach to generate the drift fields needed to provoke a faster charge collection by means of doping gradients.