Diffusion of gallium in sapphire

In this paper, the characteristics of the diffusion of gallium into sapphire are investigated by SIMS analysis, as a step towards the fabrication of optimized Ga:sapphire optical waveguides. The diffusion coefficient was obtained for temperatures between 1400 °C and 1600 °C, and the results confirm that sapphire substrates can be readily doped with gallium, to depths in the order of microns, at a temperature of 1600 °C. The procedure yields samples with low surface roughness and no apparent unwanted surface features, and the dopant concentration can be selected over a wide range, as gallium has a high solid solubility in sapphire.