Properties of low-temperature passivation of silicon with ALD Al₂O₃ films and their PV applications

Abstract

Low-temperature-deposited aluminium oxide (Al₂O₃) thin films were grown on p-type Si substrates by the remote plasma atomic layer deposition (RPALD) technique. The RPALD technique uses an alternative trimethylaluminum precursor and oxygen radicals to obtain good interface properties for metal-insulatorsemiconductor (MIS) inversion-layer solar cell applications. Si MIS capacitors with ultra-thin Al₂O₃ (film thickness ranges from 1 nm to 6 nm) gate dielectric and SiN_x films were fabricated at 300°C and at room temperature (RT), respectively. Low-temperature-deposited Al₂O₃ and SiN_x films were characterized by electrical properties such as capacitance-voltage (C-V), and current-voltage (I–V). The interface state density (D_it) of the MIS capacitors with SiN_x films and without SiN_x films was derived from the 1 MHz frequency C-V curves. By using ultra-thin RPALD Al₂O₃, RT-sputtered SiN_x films and a simple fabrication-processing sequence, MIS solar cells were fabricated on 1 Ω·cm to 10 Ω·cm p-Si wafers. The fabricated MIS solar cell with passivated Al₂O₃ and SiN_x films has 8.21% efficiency.