Thermal activation energy for the passivation of the n -type crystalline silicon surface by hydrogenated amorphous silicon

Excellent surface passivation of crystalline silicon wafers is known to occur following post-deposition thermal annealing of intrinsic a-Si:H thin-film layers deposited by plasma-enhanced chemical vapor deposition. In this work, layer thicknesses ranging from 5 to 50 nm were used to indirectly study the surface passivation mechanism by sequentially measuring the effective carrier lifetime as a function of annealing time and temperature. From this, an activation energy of 0.7±0.1 eV was calculated, suggesting that surface passivation is reaction-limited and not determined by a bulk hydrogen diffusion process. We conclude that the primary surface reaction stems from surface rearrangement of hydrogen already near the interface.