Change in atomic layer deposited Al2O3 passivation characteristics by ozone concentration

Abstract

We investigated the effect on passivation performance of ozone-based Al2O3 thin films grown by atomic layer deposition due to the increase in ozone concentration; ozone concentration was varied from 150 g/Nm3 to 330 g/Nm3. We found that the carrier lifetime and implied open-circuit voltage (iVoc) increased as the ozone concentration increased in the as-deposited condition. Although the passivation performance after annealing also improved and had a maximum value in the low ozone concentration region (<250 g/Nm3, 17 wt%), it showed a reverse trend compared to the as-deposited sample in the high ozone concentration region (>250 g/Nm3) as the ozone concentration increased. The maximum values of carrier lifetime and iVoc obtained in the low ozone concentration region are 1.4 ms and 656 mV, respectively. The improved values in the low ozone concentration region are attributed to a decrease in carbon and increase in hydrogen at the Al2O3/Si interface after forming gas annealing. As a result, the interfacial trap density in the low ozone concentration region was enhanced than that of the high ozone concentration region after annealing.