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On the determination of the emitter saturation current density from lifetime measurements of silicon devices
Author(s) -
Mäckel Helmut,
Varner Kenneth
Publication year - 2013
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.2167
Subject(s) - common emitter , saturation current , current density , materials science , silicon , doping , optoelectronics , diffusion , saturation (graph theory) , carrier lifetime , analytical chemistry (journal) , computational physics , condensed matter physics , physics , chemistry , voltage , thermodynamics , mathematics , chromatography , quantum mechanics , combinatorics
ABSTRACT Contactless photoconductance measurements are commonly used to extract the emitter saturation current density ( J oe ) for crystalline silicon samples containing an emitter on the surface. We review the physics behind the analysis of J oe and compare the commonly used approximations with more generalised solutions using two‐dimensional device simulations. We quantify errors present in such approximations for different test conditions involving varying illumination conditions and surface properties in samples with the same emitter on both sides. The simulated J oe obtained from the dark hole current from the emitter into the bulk is nearly the same as the simulated J oe determined by photoconductance measurements of the rear diffusion. The simulated J oe at the front emitter is equivalent to that at the rear emitter only when the sample is subject to a nearly constant and flat generation profile. For illumination conditions including visible light, the simulated J oe at the front emitter is smaller than the simulated J oe at the rear emitter. Both J oe at the rear emitter and from the dark hole current in the emitter remain nearly constant over a wide range of base doping densities. The approximations used for the determination of J oe from photoconductance measurements make J oe dependent on the excess minority carrier density. Lifetime measurements demonstrate that, even in high‐quality silicon, J oe should be determined from the analytical solution as a function of excess minority carrier density including Shockley‐Read‐Hall recombination. Copyright © 2012 John Wiley & Sons, Ltd.