Pressure-driven surface chemistry shift in Si:P RPCVD: From growth inhibition to catalysis

Phosphorus-doped silicon layers are at the core of Complementary Metal Oxide Semiconductors, Micro-Electro-Mechanical Systems, photonics and silicon-based quantum technologies. Yet, the role of phosphine (PH 3 ) during the reduced-pressure chemical vapor deposition (RPCVD) of Si:P with gaseous Si precursors such as SiH 4 or SiH 2 Cl 2 remains debated. Here, we systematically investigate the influence of temperature, silicon precursor chemistry and PH 3 flow on Si:P growth kinetics and doping over the 20–200 Torr range. We identify a pressure-driven PH 3 reactivity crossover, with PH 3 acting as a growth inhibitor at low pressure and exhibiting growth-enhancing behavior at pressures of 100 Torr and above, particularly around 750 °C. This growth-enhancement behavior is consistent with a catalytic or reaction-facilitating role of PH 3 -derived surface species. To quantify this behavior, we introduce a reaction-sensitivity factor, R = GR(high PH 3 flow)/GR(low PH 3 flow), which discriminates between poisoning (R < 1), transition (R ≈ 1), and catalytic (R > 1) regimes. The growth-enhancement regime is associated with a reduction in apparent activation energy, indicating a modification of the overall temperature dependence of the growth process, together with enhanced phosphorus incorporation. These observations are consistent with a pressure-dependent modification of the surface reaction environment. These findings help clarify the pressure-dependent behavior of PH 3 in RPCVD and establish pressure as a key lever for controlling both growth kinetics and dopant incorporation during Si:P epitaxy.