Low-temperature laser generated ultrathin aluminum oxide layers for effective c-Si surface passivation

In this paper, we propose and experimentally demonstrate a new laser processing method for low-temperature formation of effective aluminum oxide passivation layers on crystalline silicon. An aluminum film with a thickness of only several nm is evaporated on the silicon surface, after which a long pulse laser is utilized to convert the metal film to oxide. Laser processing parameters, especially laser energy fluence, are systematically optimized to get the critical condition to realize carrier lifetime similar to that of the bulk wafer, which we consider good passivation, while causing no damage to its surface. An effective surface recombination velocity below 25 cm s−1 is obtained right after the proper laser treatment of the Al metal film. After further annealing in forming gas, a 1.02 millisecond effective carrier lifetime as well as an effective surface recombination velocity below 13 cm s−1 is achieved for 1.4 Ω·cm n-type Si wafer.