MODELING OF THE FIELD-EMISSION MICROTRIODE WITH EMITTER COVERED WITH POROUS SILICON

Electron field emission is obtained using high enough (greater than or equal to 1 V/nm) electric fields. Such local fields are usually obtai ned using sharp emitters. An alternative approach is to cover the othe rwise blunt emitter (BE) with a porous silicon (PS) layer. The PS is c omposed of many fibrils with dimensions of several nm which act as ''n ano-emitters''. In this article such an emitter is considered as part of a vertical field emission microtriode (FEMT). The BE has spherical tip and conical body and protrudes through the gate circular opening, allowing the FEMT operation in the collector-assisted mode. An electri c field multiplication approximation is studied using both an analytic al and a numerical emitter model. The field multiplication means that the fibril increases the local electric field, which is already increa sed by the BE as compared with the uniform field at large distances fr om it. This approximation is valid as long as the fibril dimensions ar e much smaller than the BE ones. The fibrils mutual influence on the f ield is studied separately and taken into account for the FEMT case. T he emission current is computed through integration of the Fowler-Nord heim J(E) current density-electric field relationship over the BE and fibrils area. Comparison is provided with the case of BE not covered w ith PS. The emission current is obtained as function of model paramete rs. FEMT modelling results include transconductance, capacitance, cut- off frequency and static gain, Reference to experimental results is pr ovided.