dc.description.abstract | This experiment is based on electron cyclotron resonance chemical vapor deposition (ECR-CVD) to deposit boron-doped hydrogenated silicon oxide (SiO:H) films ,and investigating the structural as well as optoelectronic properties of the doping films. Furthermore, compared with conventional PECVD, ECR-CVD has several advantages, such as the excellent deposition rates, no electrode contamination, high gas utilization, low energy ion bombardment due to the property of high-density plasma. The boron-doped hydrogenated silicon oxide films with wide-gap and low resistivity were fabricated by ECR-CVD process by using SiH4 and CO2 gas mixture. In addition, this material will be applied to amorphous silicon / crystalline silicon heterojunction solar cells. Using p-SiO:H films as emitter layer can reduce the loss of the incident light and improved the short-circuit current of solar cells.
In this study, we modulated the CO2 flow rate, process pressure, B2H6 flow rate, microwave power, and hydrogen dilution ratio to investigate the thin films quality. Furthermore, the structural and optoelectronic properties of the p-SiO:H films have been characterized by using spectroscopy ellipsometry, Fourier transform infrared spectrometer, UV-Vis-NIR spectrometer, Hall measurement, and X-ray photoelectron spectrometer. The results of experiments shown that the excess oxygen atoms in the films will increase the defect and degrade the electronic properties. Thus, the control of oxygen content in the films is very important to obtain a high electronic properties. Under the modulation of working pressure and microwave power, the electronic properties were increased with the high crystallinity of the p-Si:O film. But the Si-O bonding will be broken in the condition of lower working pressure and higher microwave power. Under the modulation of B2H6 flow rate, the excess boron atoms in the films will increase the defect and degrade the electronic properties. However, the suitable amount of the boron atom can help the formation of Si-O bonding. Under the modulation of hydrogen dilution, the optical bandgap and electronic properties of p-SiO:H films can be increased in the condition of high hydrogen dilution. Under the condition of [CO2] / [SiH4] = 0.8 and [H2] / [SiH4] = 60, we obtained the optical bandgap and resistivity of the film were 1.88 eV and 9.76 × 10^-3 ohm-cm, respectively.
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