The effect of different radio-frequency powers on characteristics of amorphous boron carbon thin film alloys prepared by reactive radio-frequency plasma enhanced chemical vapor deposition

摘要

The effects of different radio-frequency (rf) powers on the characteristics of amorphous boron carbon (BC) thin film alloys on n-type silicon (n-Si) wafers prepared by reactive radio-frequency plasma enhanced chemical vapor deposition (rf-PECVD) are investigated. The reactive rf-PECVD was the combination of rf-PECVD and sputtering. Five kinds of amorphous BC thin film alloys were prepared with rf powers of 100, 200, 300, 400, and 500 W. Experimental results show that when the rf power increases from 100 to 500 W, the deposition rate of amorphous BC thin film alloys slightly decreases from 1.14 to 1.00 nm/s that is resulted from the increase of the B/C ratio. The amorphous BC thin film alloy prepared at the rf power of 300 W has a maximum graphitization degree and sp~2 carbon bonds, so it has the lowest energy band gap and electrical resistivity. All the amorphous BC thin film alloys prepared with different rf powers are p-type. When the amorphous BC thin film alloy prepared at the rf power of 300 W, the amorphous BC-Si diode possesses the lowest series resistance of 279 Ω and an ideality factor of 4.9; after annealed at 623 K, the series resistance and ideality factor of this diode reduce to 98 Ω and 2.47, respectively. When the amorphous BC thin film alloys were prepared at the rf power of 300 W, the built-in voltages of the amorphous BC-Si devices are 0.45 and 0.88 V for the amorphous BC thin film alloys before and after annealed at 623 K, respectively. When an additional native oxide of SiO_2 layer was prepared on the n-type silicon substrate surface, the power conversion efficiency and fill factor of amorphous BC/SiO_2-Si devices are 1.04% and 88.3%, respectively. Hence, the amorphous BC thin film alloys prepared by reactive rf-PECVD have the potential applied to the fabrication of solar cells.