GaAs based diffusion welded high voltage diode stacks

Abstract

The determination of technical requirements for GaAs epistructures intended for high voltage diode stacks has been made. The suitable doping level of p+ substrate was estimated by the contact resistance measurements. Analysis has shown that for the p+ substrates with the current densities about 0.5-1 A/cm2 the specific contact resistance depends weakly on doping concentration (at least in the range from 5x1018 to 1x1019cm–3). The I-V measurements showed that Al/p+−pin contacts for n-layer concentration 1x1015cm–3 have lock-type barrier causing very high voltage drops in diode stacks. For p+−pin−n+ structures the forward voltage drop depends on doping level as well as on epilayer thickness. The reverse voltage depends on pin-layer thickness only. It was found that for diode stacks the suitable doping for p+ substrate is about 5x1018cm–3 and n+ layer doping in epitaxial p+−pin−n+ GaAs structures concentration must be higher than 1x1018 cm3.