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Title: Impact of implanted phosphorus on the diffusivity of boron and its applicability to silicon solar cells

Abstract

In this work, boron diffusivity reduction in extrinsically doped silicon was investigated in the context of a process combination consisting of BBr 3 furnace diffusion and preceding Phosphorus ion implantation. The implantation of Phosphorus leads to a substantial blocking of Boron during the subsequent Boron diffusion. First, the influences of ion implantation induced point defects as well as the initial P doping on B diffusivity were studied independently. Here, it was found that not the defects created during ion implantation but the P doping itself results in the observed B diffusion retardation. The influence of the initial P concentration was investigated in more detail by varying the P implantation dose. A secondary ion mass spectrometry (SIMS) analysis of the BSG layer after the B diffusion revealed that the B diffusion retardation is not due to potential P content in the BSG layer but rather caused by the $n$-type doping of the crystalline silicon itself. Based on the observations the B diffusion retardation was classified into three groups: (i) no reduction of B diffusivity, (ii) reduced B diffusivity, and (iii) blocking of the B diffusion. The retardation of B diffusion can well be explained by the phosphorus doping level resulting inmore » a Fermi level shift and pairing of B and P ions, both reducing the B diffusivity. Besides these main influences, there are probably additional transient phenomena responsible for the blocking of boron. Those might be an interstitial transport mechanism caused by P diffusion that reduces interstitial concentration at the surface or the silicon/BSG interface shift due to oxidation during the BBr3 diffusion process. Lifetime measurements revealed that the residual (non-blocked) B leads to an increased dark saturation current density in the P doped region. Nevertheless, electrical quality is on a high level and was further increased by reducing the B dose as well as by removing the first few nanometers of the silicon surface after the BBr 3 diffusion« less

Authors:
 [1];  [1];  [2];  [1];  [1]
  1. Fraunhofer Inst. for Solar Energy Systems (ISE), Freiburg (Germany)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); German Federal Ministry for Economic Affairs and Energy; European Commission (EC)
OSTI Identifier:
1351594
Report Number(s):
NREL/JA-5K00-64954
Journal ID: ISSN 0021-8979
Grant/Contract Number:  
AC36-08GO28308; 0325292 (ForTeS); 608498 (HERCULES)
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 118; Journal Issue: 4; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; silicon; furnaces; ion implantation; silicon doping; interstitial defects

Citation Formats

Schrof, Julian, Müller, Ralph, Reedy, Robert C., Benick, Jan, and Hermle, Martin. Impact of implanted phosphorus on the diffusivity of boron and its applicability to silicon solar cells. United States: N. p., 2015. Web. doi:10.1063/1.4926764.
Schrof, Julian, Müller, Ralph, Reedy, Robert C., Benick, Jan, & Hermle, Martin. Impact of implanted phosphorus on the diffusivity of boron and its applicability to silicon solar cells. United States. doi:10.1063/1.4926764.
Schrof, Julian, Müller, Ralph, Reedy, Robert C., Benick, Jan, and Hermle, Martin. Wed . "Impact of implanted phosphorus on the diffusivity of boron and its applicability to silicon solar cells". United States. doi:10.1063/1.4926764. https://www.osti.gov/servlets/purl/1351594.
@article{osti_1351594,
title = {Impact of implanted phosphorus on the diffusivity of boron and its applicability to silicon solar cells},
author = {Schrof, Julian and Müller, Ralph and Reedy, Robert C. and Benick, Jan and Hermle, Martin},
abstractNote = {In this work, boron diffusivity reduction in extrinsically doped silicon was investigated in the context of a process combination consisting of BBr3 furnace diffusion and preceding Phosphorus ion implantation. The implantation of Phosphorus leads to a substantial blocking of Boron during the subsequent Boron diffusion. First, the influences of ion implantation induced point defects as well as the initial P doping on B diffusivity were studied independently. Here, it was found that not the defects created during ion implantation but the P doping itself results in the observed B diffusion retardation. The influence of the initial P concentration was investigated in more detail by varying the P implantation dose. A secondary ion mass spectrometry (SIMS) analysis of the BSG layer after the B diffusion revealed that the B diffusion retardation is not due to potential P content in the BSG layer but rather caused by the $n$-type doping of the crystalline silicon itself. Based on the observations the B diffusion retardation was classified into three groups: (i) no reduction of B diffusivity, (ii) reduced B diffusivity, and (iii) blocking of the B diffusion. The retardation of B diffusion can well be explained by the phosphorus doping level resulting in a Fermi level shift and pairing of B and P ions, both reducing the B diffusivity. Besides these main influences, there are probably additional transient phenomena responsible for the blocking of boron. Those might be an interstitial transport mechanism caused by P diffusion that reduces interstitial concentration at the surface or the silicon/BSG interface shift due to oxidation during the BBr3 diffusion process. Lifetime measurements revealed that the residual (non-blocked) B leads to an increased dark saturation current density in the P doped region. Nevertheless, electrical quality is on a high level and was further increased by reducing the B dose as well as by removing the first few nanometers of the silicon surface after the BBr3 diffusion},
doi = {10.1063/1.4926764},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 4,
volume = 118,
place = {United States},
year = {2015},
month = {7}
}

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