Using positron annihilation measurements we observed the formation of thermal vacancies in highly As and P doped Si. The vacancies start to form at temperatures as low as 650 K and are mainly undecorated at high temperatures. Upon cooling the vacancies form stable vacancy-impurity complexes such as $V\mathrm{\text{−}}{\mathrm{A}\mathrm{s}}_3$. We determine the vacancy formation energy of $E_f=1.1(2)\mathrm{e}\mathrm{V}$ and the migration energy of $E_m=1.2(1)\mathrm{e}\mathrm{V}$ in highly doped Si. By associating these values with the vacancy-impurity pair, we get an estimate of 2.8(3) eV for the formation energy of an isolated neutral monovacancy in intrinsic Si.

• Received 2 August 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.255502