Investigation of nature of UV induced negative charge in AI2O3 films

Aluminum oxide (Al 2 O 3 ) thin films are used for passivation of p-type silicon surface in solar cells. In this work we investigate how atomic layer deposition (ALD) and pulsed-dc (p-DC) reactive sputtered Al 2 O 3 film respond to UltraViolet (UV) illumination. UV exposure of the passivation is inevitable in the field and stability of the films to UV is an important criteria for solar cell application. We find that the negative fixed charge in the film increases upon UV illumination, leading to a better passivation. In conventional process, the film has to be annealed after deposition for the activation of the passivation. Fixed oxide charge density is found to be 5.8 × 1012 cm−2 and 9 × 1012 cm−2 for annealed and UV illuminated film respectively. So, it is proposed that annealing step can be replaced by UV illumination for activation of passivation.