GaAs based diffusion welded high voltage diode stacks

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.