title: Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures.
abstract: Thermal atomic layer-deposited (ALD) aluminum oxide (Al2O3) acquires high negative fixed charge density (Qf) and sufficiently low interface trap density after annealing, which enables excellent surface passivation for crystalline silicon. Qf can be controlled by varying the annealing temperatures. In this study, the effect of the annealing temperature of thermal ALD Al2O3 films on p-type Czochralski silicon wafers was investigated. Corona charging measurements revealed that the Qf obtained at 300°C did not significantly affect passivation. The interface-trapping density markedly increased at high annealing temperature (>600°C) and degraded the surface passivation even at a high Qf. Negatively charged or neutral vacancies were found in the samples annealed at 300°C, 500°C, and 750°C using positron annihilation techniques. The Al defect density in the bulk film and the vacancy density near the SiOx/Si interface region decreased with increased temperature. Measurement results of Qf proved that the Al vacancy of the bulk film may not be related to Qf. The defect density in the SiOx region affected the chemical passivation, but other factors may dominantly influence chemical passivation at 750°C.
authors: Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China. zhouchl@mail.iee.ac.cn.
authors: Yan
authors: Y
authors: Zhao
authors: Chunlan
authors: C
authors: Zhou
authors: Xiang
authors: X
authors: Zhang
authors: Peng
authors: P
authors: Zhang
authors: Yanan
authors: Y
authors: Dou
authors: Wenjing
authors: W
authors: Wang
authors: Xingzhong
authors: X
authors: Cao
authors: Baoyi
authors: B
authors: Wang
authors: Yehua
authors: Y
authors: Tang
authors: Su
authors: S
authors: Zhou