Ultrathin SiO2/Al2O3 passivation for silicon heterojunctions using rapid thermal annealing

In this manuscript we study the surface passivation properties of ultrathin Al 2 O 3 in silicon heterojunctions. The Al 2 O 3 layer needs to be thin enough ( 2 O 3 shows that thicknesses below 10nm do not provide adequate surface passivation. In this work, we combine 0.8 nm of Al 2 O 3 with 1nm of SiO 2 to improve the passivation properties of the thin Al 2 O 3 . The SiO 2 helps to improve the chemical passivation by increasing the storage capacity of hydrogen with Al 2 O 3 , and the overall negative fixed charge of the SiO 2 /Al 2 O 3 stack. Additionally, we have optimized the rapid thermal annealing in forming gas environment to activate the Al 2 O 3 in the SiO 2 /Al 2 O 3 stack. To further increase the hydrogen in the films we deposited n-a-Si:H film before the annealing step. Effective minority-carrier lifetimes of 5 ms and implied open-circuit voltages of 723 mV were accomplished.