Heavily doped bulk unipolar structures

Abstract

Transport properties of bulk unipolar (barrier) devices are investigated in the steady-state mode. This has entailed the study of heavily doped silicon characteristic which comprises important regions of the multilayer bulk unipolar devices. The devices covered are Camel diodes, P-plane barrier diodes and open-base bipolar transistors. Two operating modes are distinguished: the punchthrough mode, and the non punch-through (bipolar) mode. A combination of thermionic and diffusion mechanisms is used in the current - voltage analysis. Minority carrier transport at the polysilicon - monosilicon interface is also studied in polysilicon emitter bulk unipolar diodes with the emphasis having been placed on the influence of heavy doping; the aim being the development of a useful predictive tool for the study of these structures in which transistor action can be obtained due to the mechanism of barrier height modulation via minority-carrier injection. The validity of the analysis is evaluated by comparison with available experimental results. A new form of multigrain - barrier bulk unipolar diode structure has been proposed and analyzed using the carrier trapping model at the grain boundary of the polysilicon. Heavy doping effects / parameters are included in the developed analysis. As it stands, the present model helps in fulfilling the purpose of giving an insight into the physical mechanism of charge carrier transport with heavy doping at a fundamental level and providing a tool for the examination of the behaviour of alternative device configurations. However, heavy doping effects are revealed as being of profound importance in the determination of bulk unipolar device characteristics