Dopant Diffusion in Silicon. III. Acceptors

Aluminum, gallium, indium, and thallium acceptors have been diffused into (111) silicon from doped epitaxially deposited source layers in a flowing hydrogen atmosphere. As in the case of P, As, Sb, and Bi donors reported earlier, all these acceptors show significantly lower mobilities when freed from surface effects. The temperature dependence of the intrinsic diffusion coefficients, obtained above 1120 °C, are characterized by the following preexponential and activation-energy parameters: 1.385, 0.374, 0.785, (1.37) ${\mathrm{cm}}^2$/sec, and 3.41, 3.39, 3.63, (3.70) eV/atom for Al, Ga, In, Tl, respectively. An analysis of these diffusion characteristics indicate a similar point-defect mechanism for both group-III and group-V dopants in silicon.