Reduction of carrier reflection effects in a silicon MBE p+-s-n+ device using cascaded end regions

The results of a steady-state numerical analysis of thin p+-n-n+ devices in silicon are reported. Successful fabrication of such devices by MBE has recently been reported in the literature. Asymmetric doping of the end regions causes either of the carrier types (majority or minority) to dominate the forward current. Both the carriers are reflected by the opposite junctions. The reflection of the dominant carriers has a pronounced effect on the forward current in low- and medium-level injections. To investigate further the junction reflection properties, devices with cascaded end regions are analysed. It is found that on making the reflecting end region a cascade of two steps, of concentrations 1×1018 cm-3 and 1 × 1016 cm-3, respectively, the forward current increases by more than 50% in typical operating regions.