Spatially Resolved Diffusion of Aluminum in 4H-SiC during Postimplantation Annealing

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The fabrication of power semiconductor devices based on 4H-silicon carbide (SiC) typically includes doping by ion implantation and postimplantation annealing to activate the implanted dopants. The high-Temperature annealing process can initiate various diffusion mechanisms that alter the initial implantation profile in terms of spatial distribution and doping concentration. To investigate the diffusion of aluminum, the main p-dopant in 4H-SiC, samples are prepared by ion implantation and subsequent annealing at 1650 °C for 30 min. Secondary ion mass spectrometry (SIMS) measurements before and after the annealing process are performed to monitor the aluminum concentration. A significant amount of aluminum moves toward the surface and into the lateral direction, which is shown to be directly related to the implantation-induced point defects. Transmission electron microscopy (TEM) images support the discussion of diffusion mechanisms and their dependence on the defect type.