Electrical isolation of a silicon [Delta]-doped layer in GaAs by ion irradiation

Abstract

The electrical isolation of a n-type d -doped layer embedded into undoped GaAs was studied using proton or helium ion bombardment. The threshold dose for isolation Dth of the d -doped layer was found to be '2 times higher than that predicted for thick doped layers of similar carrier concentration. The thermal stability of the isolation, i.e., the persistence of sheet resistance Rs at values .109V/h after subsequent thermal annealing, is limited to temperatures below 400 °C. This temperature limit for the thermal stability Tsm is markedly lower than those observed in wider doped layers in which Tsm is >650 °C. A previously isolated d -doped layer presents p-type conductivity after annealing at temperatures .600 °C .