Atomic-scale insights of platinum diffusion doping in silicon-based power semiconductors: a first-principles study

Abstract Fast recovery diodes are silicon-based power diodes characterized by their good switching properties and short reverse recovery time. Doping platinum (Pt) in the PN junction region of the fast recovery diode to form substitution Pt atoms can provide ideal recombination centers to facilitate the rapid recombination of minority carriers, improve the switching speed of the device and reduce its reverse loss power. Since the formation of substitution atoms in specific regions is required, this work have investigated the atomic-scale mechanisms of Pt doping by diffusion: migration of Pt atoms through interstitial sites and the formation of substitution atoms. The results show that Pt atoms migrate in silicon through the most stable interstitial sites (hexagonal interstitial sites, H) and then migrate isotropic in the following six directions and their inverses: [110], [1 1 ¯ 0], [101], [10 1 ¯ ], [011] and [01 1 ¯ ], and the diffusion coefficient is D = 8.94 × 10 − 9 exp ( − 0.19 eV K B T ) ( m 2 / s − 1 ) . The formation of substitution Pt in silicon predominantly requires vacancies, as the kick-out mechanism is hindered by a high energy barrier. This work reveals a new, low-barrier pathway in which a Pt atom (at the second-nearest H of vacancy) pushes a nearby vacancy-adjacent Si atom into the vacancy, subsequently occupying the released lattice site. This newly discovered process is distinct from the conventional Frankel–Turnbull mechanism, in which the Pt atom (at the first-nearest H of vacancy) directly migrates into the vacancy. The pathway is determined by the specific migration route taken by Pt when approaching the vacancy. The results obtained facilitate the comprehension and exploration of the micro-mechanism of Pt doping in silicon-based power semiconductors.