Depth profiles of thermal donors formed at 450 degrees C in oxygen-rich n-type silicon

Depth profiles of thermal donors formed at 450 degrees C in oxygen-rich n-type silicon have been studied through capacitance-voltage measurements of Au Schottky diodes in the oxygen concentration range 8.1*10¹⁷ to 15.3*10¹⁷ cm^-3. Thermal donor concentrations increase with depth and their depth profiles are empirically fitted to the error function equation. The obtained diffusivity decreases with annealing time and is higher for samples with lower initial oxygen concentrations. Combining with the infrared absorption measurements, it is found that the curves of the diffusivity as a function of loss of interstitial oxygen coincide with each other. A similar tendency is observed for the oxygen diffusivity evaluated with secondary-ion mass spectrometry. These results indicate that depth profiles of thermal donors are caused by both the out-diffusion and clustering of oxygen.