Electrical isolation of a silicon delta-doped layer in GaAs by ion irradiation

The electrical isolation of a n-type delta-doped layer embedded into undope d GaAs was studied using proton or helium ion bombardment. The threshold do se for isolation D-th of the delta-doped layer was found to be approximate to 2 times higher than that predicted for thick doped layers of similar car rier concentration. The thermal stability of the isolation, i.e., the persi stence of sheet resistance R-s at values > 10(9)Omega/square after subseque nt thermal annealing, is limited to temperatures below 400 degrees C. This temperature limit for the thermal stability T-sm is markedly lower than tho se observed in wider doped layers in which T-sm is congruent to 650 degrees C. A previously isolated delta-doped layer presents p-type conductivity af ter annealing at temperatures > 600 degrees C . (C) 1999 American Institute of Physics. [S0003-6951(99)03639-6].