Al2O3 thin films deposited by thermal atomic layer deposition: Characterization for photovoltaic applications

Al2O3 thin films with thickness between 2 and 100nm were synthetized at 250°C by thermal atomic layer deposition on silicon substrates. Characterizations of as-deposited and annealed layers were carried out using ellipsometry, X-ray reflectivity, and X-ray photoelectron spectroscopy. A silicon-rich SiOx layer at the interface between Si and Al2O3 was introduced in the optical models to fit the experimental data. Surface passivation performances of Al2O3 layers deposited on n-type float-zone monocrystalline silicon were investigated as a function of thickness and post-deposition annealing conditions. Surface recombination velocity around 2cm.s−1 was measured after the activation of the negative charges at the Si/Al2O3 interface under optimized annealing at 400°C for 10min. The evolution of the interface layer and of the material properties with the thermal treatment was studied. •We characterize atomic layer deposited Al2O3 thin films on silicon substrates.•Abrupt transition between silicon and Al2O3 was not compatible with our results.•A silicon-rich SiOx layer was present at the interface between silicon and Al2O3.•Very low surface recombination velocity (2cm.s−1) was measured after annealing.•Al2O3 layer properties were stable after annealing at 400°C for 10min.