p{sup +}-doping analysis of laser fired contacts for silicon solar cells by Kelvin probe force microscopy

Journal Article · Mon Mar 14 04:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4943064· OSTI ID:22596892

Sommer, D.; Fritz, S.; Schiele, Y.; Hahn, G.; Terheiden, B. ^[1]

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1. Department of Physics, University of Konstanz, 78457 Konstanz (Germany)

Local rear contacts for silicon passivated emitter and rear contact solar cells can be established by point-wise treating an Al layer with laser radiation and thereby establishing an electrical contact between Al and Si bulk through the dielectric passivation layer. In this laser fired contacts (LFC) process, Al can establish a few μm thick p{sup +}-doped Si region below the metal/Si interface and forms in this way a local back surface field which reduces carrier recombination at the contacts. In this work, the applicability of Kelvin probe force microscopy (KPFM) to the investigation of LFCs considering the p{sup +}-doping distribution is demonstrated. The method is based on atomic force microscopy and enables the evaluation of the lateral 2D Fermi-level characteristics at sub-micrometer resolution. The distribution of the electrical potential and therefore the local hole concentration in and around the laser fired region can be measured. KPFM is performed on mechanically polished cross-sections of p{sup +}-doped Si regions formed by the LFC process. The sample preparation is of great importance because the KPFM signal is very surface sensitive. Furthermore, the measurement is responsive to sample illumination and the height of the applied voltage between tip and sample. With other measurement techniques like micro-Raman spectroscopy, electrochemical capacitance-voltage, and energy dispersive X-ray analysis, a high local hole concentration in the range of 10{sup 19 }cm{sup −3} is demonstrated in the laser fired region. This provides, in combination with the high spatial resolution of the doping distribution measured by KPFM, a promising approach for microscopic understanding and further optimization of the LFC process.

• OSTI ID: 22596892
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 10 Vol. 119; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC FORCE MICROSCOPY
CAPACITANCE
CONCENTRATION RATIO
DIELECTRIC MATERIALS
DOPED MATERIALS
ELECTRIC CONTACTS
ELECTRIC POTENTIAL
ELECTROCHEMISTRY
FERMI LEVEL
HOLES
LASER RADIATION
LASERS
RAMAN SPECTROSCOPY
SILICON
SILICON SOLAR CELLS
SPATIAL RESOLUTION
TWO-DIMENSIONAL CALCULATIONS
X RADIATION