We demonstrate in this paper that in-situ optical probes could provide valuable information to the MOCVD process of AlGaN. It is shown that a single-beam optical reflectance monitor can be used to extract growth rates and consequently the incorporation efficiency of column III eleements, which in turn enables real-time monitoring of the extent of gas-phase parasitic reactions among TMAl, TMGa, and NH_3. Furthermore, we have employed a multiple-beam reflectance probe to measure wafer curvature during growth. The information of wafer curvature is converted to the product of the stress and thicness of AlGaN films, which can be used to monitor the strain during the growth of AlGaN on sapphire. We also present preliminary data of strain contrl using different buffer layer schemes.
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