Improvement of passivation performance of silicon nanocrystal/silicon oxide compound layer by two-step hydrogen plasma treatment

A two-step hydrogen plasma treatment (HPT) is carried out for Si nanocrystals/silicon oxide compound passivating contacts to improve their passivation perfor-mance. The 2-step HPT consists of a first HPT at a high temperature of 500 degrees C and a second HPT at a lower temperature of 300 degrees C. Etching of n-type polycrystalline Si (n+-poly-Si) is suppressed by using low RF power and short duration as the condition for the second HPT. For the passivating contact with thin n+-poly-Si, the implied open-circuit voltage (i-VOC) was improved to 723 mV after the 2-step HPT, which is higher than the i-VOC after the one-step HPT (718 mV) owing to enhanced hydrogenation of the Si nanocrystals/silicon oxide compound layer. On the other hand, 1.4-fold larger contact resistivity (rho c) was obtained after the 2-step HPT. This increase in rho c is probably attributed to the suppression of trap-assisted tunneling. The largest i-VOC value of 744 mV and the lowest rho c value of 12 m omega cm2 was observed for the contact with 300-nm-thick n+-poly-Si, possibly due to enhanced field-effect passivation after the 2-step HPT.

Automated summary

A two-step hydrogen plasma treatment was used to improve the passivation performance of Si nanocrystals/silicon oxide compound passivating contacts. This treatment enhanced the hydrogenation of the Si nanocrystals/silicon oxide compound layer, leading to an improved implied open-circuit voltage. However, it also resulted in an increase in contact resistivity.