TY - JOUR

T1 - Elucidation of Iron Gettering Mechanisms in Boron-Implanted Silicon Solar Cells

AU - Laine, Hannu S.

AU - Vahanissi, Ville

AU - Liu, Zhengjun

AU - Magana, Ernesto

AU - Krugener, Jan

AU - Morishige, Ashley E.

AU - Salo, Kristian

AU - Lai, Barry

AU - Savin, Hele

AU - Fenning, David P.

N1 - Funding information: This work used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. The work of V. Vähänissi, Z. Liu, K. Salo, and H. Savin was supported in part by the Finnish Funding Agency for Innovation under project “BLACK” (Project 2956/31/2014), Academy of Finland, in part by Okmetic Oyj, and in part by Semilab, Inc. The work of H. S. Laine was supported in part by the Fulbright Technology Industries of Finland grant, in part by the Finnish Cultural Foundation, in part by the Walter Ahlström Foundation, in part by the Tiina and Antti Herlin Foundation, in part by Finnish Funding Agency for Innovation under project “BLACK” (Project 2956/31/2014), Academy of Finland, in part by Okmetic Oyj, and in part by Semilab, Inc. The work of E. Magaña and D. P. Fenning was supported by start-up funds from the University of California, San Diego, La Jolla, CA, USA. (Corresponding author: David P. Fenning.) H. S. Laine, V. Vähänissi, Z. Liu, K. Salo, and H. Savin are with the Department of Electronics and Nanoengineering, Aalto University, Espoo 02150, Finland (e-mail: hannu.laine@aalto.fi; ville.vahanissi@aalto.fi; zhengjun.liu@ aalto.fi; kristian.salo@aalto.fi; hele.savin@aalto.fi).

PY - 2017/12/15

Y1 - 2017/12/15

N2 - To facilitate cost-effective manufacturing of boronimplanted silicon solar cells as an alternative to BBr3 diffusion, we performed a quantitative test of the gettering induced by solartypical boron-implants with the potential for low saturation current density emitters (<50 fA/cm2).We showthat depending on the contamination level and the gettering anneal chosen, such boronimplanted emitters can induce more than a 99.9% reduction in bulk iron point defect concentration. The iron point defect results as well as synchrotron-based nano-X-ray-fluorescence investigations of iron precipitates formed in the implanted layer imply that, with the chosen experimental parameters, iron precipitation is the dominant gettering mechanism, with segregation-based gettering playing a smaller role. We reproduce the measured iron point defect and precipitate distributions via kinetics modeling. First, we simulate the structural defect distribution created by the implantation process, and then we model these structural defects as heterogeneous precipitation sites for iron. Unlike previous theoretical work on gettering via boron- or phosphorus-implantation, our model is free of adjustable simulation parameters. The close agreement between themodel and experimental results indicates that the model successfully captures the necessary physics to describe the iron gettering mechanisms operating in boron-implanted silicon. This modeling capability allows high-performance, cost-effective implanted silicon solar cells to be designed.

AB - To facilitate cost-effective manufacturing of boronimplanted silicon solar cells as an alternative to BBr3 diffusion, we performed a quantitative test of the gettering induced by solartypical boron-implants with the potential for low saturation current density emitters (<50 fA/cm2).We showthat depending on the contamination level and the gettering anneal chosen, such boronimplanted emitters can induce more than a 99.9% reduction in bulk iron point defect concentration. The iron point defect results as well as synchrotron-based nano-X-ray-fluorescence investigations of iron precipitates formed in the implanted layer imply that, with the chosen experimental parameters, iron precipitation is the dominant gettering mechanism, with segregation-based gettering playing a smaller role. We reproduce the measured iron point defect and precipitate distributions via kinetics modeling. First, we simulate the structural defect distribution created by the implantation process, and then we model these structural defects as heterogeneous precipitation sites for iron. Unlike previous theoretical work on gettering via boron- or phosphorus-implantation, our model is free of adjustable simulation parameters. The close agreement between themodel and experimental results indicates that the model successfully captures the necessary physics to describe the iron gettering mechanisms operating in boron-implanted silicon. This modeling capability allows high-performance, cost-effective implanted silicon solar cells to be designed.

KW - Boron implantation

KW - Gettering

KW - Iron

KW - Silicon

KW - Simulation

UR - http://www.scopus.com/inward/record.url?scp=85038821318&partnerID=8YFLogxK

U2 - 10.1109/JPHOTOV.2017.2775159

DO - 10.1109/JPHOTOV.2017.2775159

M3 - Article

AN - SCOPUS:85038821318

VL - 8

SP - 79

EP - 88

JO - IEEE journal of photovoltaics

JF - IEEE journal of photovoltaics

SN - 2156-3381

IS - 1

ER -