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Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks.

Xiang Y, Zhou C, Jia E, Wang W - Nanoscale Res Lett (2015)

Bottom Line: For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used.Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives.In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Beiertiao, Zhongguancun, Beijing, 100190 China.

ABSTRACT
In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(-2) eV(-1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(-2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

No MeSH data available.


Related in: MedlinePlus

Schematic representation of sample preparation.
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Fig1: Schematic representation of sample preparation.

Mentions: For the a-Si/Al2O3 stack passivation samples, 125 mm × 125 mm 0.9-Ω · cm phosphorus-doped solar grade mono-crystalline silicon(100) wafers (Jinglong Industry and Commerce Group Co. Ltd., Xingtai, Hebei Province, China) were used as substrates. The wafers were polished in KOH solution (Arkonic Gases & Chemicals Inc., Wuhu, Anhui Province, China) to a thickness of 160 μm and cleansed by a hydrogen fluoride (HF) solution (Arkonic Gases & Chemicals Inc., Wuhu, Anhui Province, China) to remove the native oxide layer. a-Si:H(i) films with thicknesses of 80 and 170 nm were deposited on just one side of the Si wafers by PECVD at 160°C using hydrogen (H2) and silane (SiH4) as precursor gases. Those films were annealed at 250°C for 10 min in air. For the reference Al2O3 single layer passivation samples, Ф100-mm polished n-type high quality silicon wafers were used as substrates. All the wafers were cleaned by H2SO4:H2O2 solution (4:1 vol) at 80°C. Before the Al2O3 film deposition, the native oxide layer present on the wafer surfaces was also removed using an HF solution. For the Al2O3 film deposition, both plasma-enhanced atomic layer deposition (PE-ALD) and thermal atomic layer deposition (T-ALD) were used. The ALD substrate temperatures were 200°C for the a-Si/Al2O3 stacks, while 100°C and 200°C for Al2O3 single layers. Al(CH3)3 (trimethylaluminum, TMA; Jiangsu Nata Opto-electronic Material Co., Ltd., Suzhou, Jiangsu Province, China) served as Al precursor, and either remote O plasma (for PE-ALD) or H2O (for T-ALD) was used as O precursor. After Al2O3 layer deposition, all the samples (both the Al2O3 single layers and the a-Si/Al2O3 stacks) were annealed at 450°C for 10 min in air. In addition, only the Al2O3 single layer passivation samples were covered with Al2O3 films (Jiangsu Nata Opto-electronic Material Co., Ltd., Suzhou, Jiangsu Province, China) on both sides of Si wafers. The sample preparation process was shown in Figure 1. The thickness of films was measured by a step profiler. The composition of Al2O3 films was measured by XPS (Beijing Synchrotron Radiation Facility, Beijing, China) before and after annealing. The interface trap density spectra were obtained from a non-contact corona C-V technique for a-Si single films and a-Si:H(i)/Al2O3 stacks (Institute of Electrical Engineering, CAS, Beijing, China) coating Si surface.Figure 1


Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks.

Xiang Y, Zhou C, Jia E, Wang W - Nanoscale Res Lett (2015)

Schematic representation of sample preparation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385324&req=5

Fig1: Schematic representation of sample preparation.
Mentions: For the a-Si/Al2O3 stack passivation samples, 125 mm × 125 mm 0.9-Ω · cm phosphorus-doped solar grade mono-crystalline silicon(100) wafers (Jinglong Industry and Commerce Group Co. Ltd., Xingtai, Hebei Province, China) were used as substrates. The wafers were polished in KOH solution (Arkonic Gases & Chemicals Inc., Wuhu, Anhui Province, China) to a thickness of 160 μm and cleansed by a hydrogen fluoride (HF) solution (Arkonic Gases & Chemicals Inc., Wuhu, Anhui Province, China) to remove the native oxide layer. a-Si:H(i) films with thicknesses of 80 and 170 nm were deposited on just one side of the Si wafers by PECVD at 160°C using hydrogen (H2) and silane (SiH4) as precursor gases. Those films were annealed at 250°C for 10 min in air. For the reference Al2O3 single layer passivation samples, Ф100-mm polished n-type high quality silicon wafers were used as substrates. All the wafers were cleaned by H2SO4:H2O2 solution (4:1 vol) at 80°C. Before the Al2O3 film deposition, the native oxide layer present on the wafer surfaces was also removed using an HF solution. For the Al2O3 film deposition, both plasma-enhanced atomic layer deposition (PE-ALD) and thermal atomic layer deposition (T-ALD) were used. The ALD substrate temperatures were 200°C for the a-Si/Al2O3 stacks, while 100°C and 200°C for Al2O3 single layers. Al(CH3)3 (trimethylaluminum, TMA; Jiangsu Nata Opto-electronic Material Co., Ltd., Suzhou, Jiangsu Province, China) served as Al precursor, and either remote O plasma (for PE-ALD) or H2O (for T-ALD) was used as O precursor. After Al2O3 layer deposition, all the samples (both the Al2O3 single layers and the a-Si/Al2O3 stacks) were annealed at 450°C for 10 min in air. In addition, only the Al2O3 single layer passivation samples were covered with Al2O3 films (Jiangsu Nata Opto-electronic Material Co., Ltd., Suzhou, Jiangsu Province, China) on both sides of Si wafers. The sample preparation process was shown in Figure 1. The thickness of films was measured by a step profiler. The composition of Al2O3 films was measured by XPS (Beijing Synchrotron Radiation Facility, Beijing, China) before and after annealing. The interface trap density spectra were obtained from a non-contact corona C-V technique for a-Si single films and a-Si:H(i)/Al2O3 stacks (Institute of Electrical Engineering, CAS, Beijing, China) coating Si surface.Figure 1

Bottom Line: For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used.Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives.In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, Chinese Academy of Sciences, No. 6 Beiertiao, Zhongguancun, Beijing, 100190 China.

ABSTRACT
In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(-2) eV(-1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(-2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

No MeSH data available.


Related in: MedlinePlus