Gallium self-diffusion in gallium phosphide

Ga self-diffusion in gallium phosphide (GaP) is measured directly in isotopically controlled GaP heterostructures. Secondary ion mass spectroscopy (SIMS) is used to monitor intermixing of ${}^{69}\mathrm{Ga}$ and ${}^{71}\mathrm{Ga}$ between isotopically pure GaP epilayers which are grown by molecular beam epitaxy (MBE) on GaP substrates. The Ga self-diffusion coefficient in undoped GaP is determined to be D=2.0 ${\mathrm{cm}}^{\mathrm{2}}{\mathrm{\hspace{0.17em}s}}^{\mathrm{-1}}$ $\exp \text{(−4.5\hspace{0.17em}}\mathrm{eV}{\mathrm{/k}}_{\mathrm{B}}\mathrm{T)}$ between 1000 and 1190 °C under phosphorus-rich condition. The self-diffusion entropy is found to be ∼4 $k_{\mathrm{B}}.$