The upper limits of useful n- and p-type doping in GaAs and AlAs

The maximum carrier concentration found for GaAs:Si is nMAX∼2×1019 cm−3, limited by the amphoteric behaviour of the Si impurities, the generation of gallium vacancies and Si precipitation. After annealing, a more typical concentration is 4–5×1018 cm−3. GaAs:C doped to a level greater than pMAX∼1019 cm−3 is unstable during post-growth heat treatments, with the formation of CC dimers that are deep donors. This process also occurs in AlAs, but pMAX has not been determined.