Negative charge material, ${\mathrm{AlO}}_{\mathrm{x}}{\mathrm{N}}_{\mathrm{y}}$ , has been fabricated to passivate the surface of p-type silicon. The fabrication of ${\mathrm{AlO}}_{\mathrm{x}}{\mathrm{N}}_{\mathrm{y}}$ was possible by using ion beam sputtering deposition to deposit AlN thin film on the surface of a p-type silicon wafer and following annealing in oxygen ambient. Capacitance-voltage analysis shows the fixed charge density has increased from ${10}^{11}{\mathrm{cm}}^{-2}$ to $2.26\times {10}^{12}{\mathrm{cm}}^{-2}$ after annealing. The solar cell efficiency increased from 15.9% to 17.3%, which is also equivalent to the reduction of surface recombination velocity from $1\times {10}^5$ to 32 cm/s.