K. Arafune

Study on surface passivation by YZO/AlO x stacking double layer for crystalline Si solar cells

We investigated stacking double layer structure, the Y₂O₃-ZrO₂ composite film (YZO) on AlO_x, for the field effect passivation with high negative fixed charge densities on p-type Si. The composition spread YZO films were deposited at room temperature by using combinatorial sputtering technique. The fixed charge densities were extracted from the flat band voltage shift in the capacitance-voltage characteristics. The as-deposited ZrO₂ film incorporated with 15% Y₂O₃ stacking on the ALD AlO_x structure showed the highest negative fixed charge of -1.9 × 10¹² cm^-2. The field effect passivation can be controlled by the negative fixed charges in the YZO film depending on the composition and dipole uniformly formed at AlO_x/Si interface. After annealing in the oxygen atmosphere, passivation properties deteriorated caused by the Al diffusion at the YZO/AlO_x interface.

Behaviors of Fe and Ni at crystal defects in multi-crystalline silicon by intentional contamination and phosphorus gettering

We investigated behaviors of Fe and Ni at crystalline defects in multi-crystalline silicon by intentional contamination and phosphorus (P) gettering processes. After contaminations, EBIC contrasts became stronger at Σ27 and Random grain boundaries (GBs), and at small-grain boundaries (SA-GBs) with >; 1° misorientation angles. After P gettering processes, EBIC contrasts recovered as low as those before metal contamination at most GBs and SA-GBs. However, some Σ27, Random GBs and SA-GBs with >;1° misorientation angle remain high contrast. Defect properties such as boundary orientations or tilt and twist components consisting misorientation angles might affect on the minority carrier recombination.

EBIC Study on Metal Contamination at Intra Grain Defects in Multicrystalline Silicon for Solar Cells

Interactions between intra-grain defects and metal impurities in multicrystalline silicon (mc-Si) were evaluated. After metal contaminations, EBIC contrasts at > 1.5o SA-GBs were more enhanced than those at Ni/1000 oC > Ni/600 oC. These results might attribute to Fe atoms form deeper energy levels of recombination centers than Ni atoms and the gettering abilities at SA-GBs depend on the misorientation angles. Many dark spots were observed in EBIC images in the Ni/600 oC. Since the dark spots corresponded to the etch pits, the dark spots might be dislocations decorated with Ni. The gettering abilities of SA-GBs depended on the misorientaion angles, and the recombination properties at SA-GBs and dark spots, such as small defects after metal contamination were different by annealing temperatures and the types of metal impurities.

Impurities distribution and recombination activity in as-grown and annealed multicrystalline silicon

To study the impact of annealing on the impurities distribution and the recombination activity of multicrystalline silicon, the synchrotron-based x-ray analysis, the electron beam induced current, and the photoluminescence mapping of near band edge and 0.78 eV deep emission were performed before and after annealing. Nickel agglomerates existed along random grain boundaries; while not along most of coincidence cite lattice grain boundaries (3,  9 and  27a) and some of random grain boundaries. At most of the recombination active grain boundaries, the existence of nickel agglomerates was indicated.

Influence of Post-Deposition Annealing on the Passivation Quality of Room Temperature Atomic Layer Deposited Aluminum Oxide

This work investigates the influence of post-deposition annealing treatments on the interface properties, such as fixed charge density (Qf) and interface trap density (Dit), of AlOx films deposited on single crystalline Si at room temperature by O3-based batch atomic layer deposition technique. We found that PDA in atomic hydrogen can significantly increase negative Qf in 10 nm-thick AlOx films by enhancing structural and chemical reorganization in the interlayer. In addition, we also found that nitrogen ions can effectively remove or passivate dominant positive fixed charges in 10 nm-thick AlOx films. Finally, we demonstrated that PDA in N2 plasma is effective technique to enhance the interface properties of 30 nm-thick AlOx films as indicated by the significantly reduced Dit down to 6.610 11 cm -2 ·eV -1 with negative Qf ≥ 10 12 cm -2 .

Atomic Layer Deposited Aluminum Oxide Passivation Layers for Crystalline Silicon: Effects of Deposition Temperature on Film and Interface Structures

1 Meiji Univ., 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan Phone: +81-44-934-7352 E-mail: tz10021@meiji.ac.jp 2 Univ. of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan 3 Tokyo Electron Ltd., 5-3-1 Akasaka, Minato-ku, Tokyo, 107-6325, Japan 4 National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan 5 JST-CREST, 4-1-8 Hontyou, Kawaguchi, Saitama, 332-0012, Japan