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 5 × 1018 to 1 × 1019 cm-3). The I-V measurements showed that Al/p+-pin contacts for n-layer concentration 1 × 1015 cm-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 5 × 1018 cm-3 and n+ layer doping in epitaxial p+-pin-n+ GaAs structures concentration must be higher than 1 × 1018 cm3.