Effect of Arsenic Partial Pressure on Capless Anneal of Ion‐Implanted GaAs

A capless anneal of ion‐implanted GaAs was performed under different partial pressure of arsenic controlled by decomposition of arsine. Sheet carrier concentration of GaAs implanted with Mg or Si increased with increasing arsenic partial pressure, while that of S + implanted showed an opposite trend which corresponded to the different lattice sites occupied in the crystal. The site‐occupation rate and ionization rate of implanted impurity atoms were thermodynamically determined by analyzing the variation of the sheet carrier concentration with the partial pressure of arsine. The site‐occupation rate was found to be larger than 90% for the case of Mg or S implantation. The ionization rate of the substitutional atoms limited the doping efficiency of implanted impurities in these cases, while both the site‐occupation rate and the ionization rate were responsible for the doping efficiency of Si implantation.