Current-controlled growth,segregation and amphoteric behavior of Si IN GaAs from Si-doped solutions

An unusual behavior of the growth kinetics and the segregation of Si during current-controlled LPE of GaAs is reported. The growth velocity (for a fiven current density) decreased by about two orders of magnitude from a value higher to a value smaller than that found in undoped solutions as the growth temperature decreased from 975 to 850°C; at 825°C dissolution of the substrate took place and a reversed current polarity was required for growth. At the same temperature range the growth velocity from undoped solutions decreased by a factor of only 3. Similarly, a two orders of magnitude decrease of the silicon segregation coefficient was observed for the same temperature change compared to changes by a factor or two in the thermally grown layers. For a given growth temperature (900°C) a change in conductivity from p- to n-type took place in the grown layers as the current density was increased. These findings were accounted for with a qualitative model based on the presence in the solution of different charged complexes containing silicon with different electromigrating characteristics. According to this model, the behavior of Si as p- and as n-type dopant (amphoteric dopant) in GaAs is related to the existence in the solution of the different charged complexes containing silicon.