Electronic passivation of silicon surfaces by thin films of atomic layer deposited gallium oxide

This paper proposes the application of gallium oxide (Ga2O3) thin films to crystalline silicon solar cells. Effective passivation of n- and p-type crystalline silicon surfaces has been achieved by the application of very thin Ga2O3 films prepared by atomic layer deposition using trimethylgallium (TMGa) and ozone (O3) as the reactants. Surface recombination velocities as low as 6.1 cm/s have been recorded with films less than 4.5 nm thick. A range of deposition parameters has been explored, with growth rates of approximately 0.2 A/cycle providing optimum passivation. The thermal activation energy for passivation of the Si-Ga2O3 interface has been found to be approximately 0.5 eV. Depassivation of the interface was observed for prolonged annealing at increased temperatures. The activation energy for depassivation was measured to be 1.9 eV.