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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/18812

Title: Kerfless layer-transfer of thin epitaxial silicon foils using novel multiple layer porous silicon stacks with near 100% detachment yield and large minority carrier diffusion lengths
Authors: Radhakrishnan, Hariharsudan Sivaramakrishnan
Martini, Roberto
Depauw, Valerie
Van Nieuwenhuysen, Kris
Bearda, Twan
Gordon, Ivan
Szlufcik, Jozef
Issue Date: 2015
Abstract: Two important aspects for the success of the porous silicon-based layer transfer method in producing kerfless thin (< 50 mu m) silicon foils for future silicon solar modules are addressed in this work: achieving high detachment yield and high minority carrier diffusion lengths. The detachment characteristics of the porous silicon-based lift-off process is studied using finite element modeling as well as experiments. It is shown that for easy detachment and high detachment yield, a low density of thin silicon pillars must be attained in the high porosity detachment layer (HP-DL) after high temperature sintering. This is elegantly achieved by increasing the thickness of the low porosity template layer (LP-TL) which acts as the vacancy supply to increase the post-anneal porosity of the HP-DL In this way, near 100% detachment yield has been achieved. However, a thicker LP-TL results in a poorer quality epitaxial growth surface. To circumvent this trade-off, novel triple and quadruple layer porous silicon stacks are introduced which decouple the function of the LP-TL that acts as both the template for epitaxy and as the vacancy supply for the HP-DL In these new stacks, a surface zone of very low void size and density (nearly void-free) is created which allows high quality epitaxy on easily-detachable porous silicon stacks. Minority carrier lifetime measurements on epitaxial foils grown on such a triple layer stack has resulted in an effective lifetime of similar to 350 mu s at the injection level of 10(15) cm(-3) which corresponds to a minimum minority carrier diffusion length of similar to 670 mu m (> 16 times the silicon thickness). With such high quality epitaxial foils combined with high detachment yield, very high efficiency solar devices on thin silicon substrates would be a reality in the near future. (C) 2014 Elsevier B.V. All rights reserved.
Notes: Corresponding author. Tel.: 032 16 28 1173/32 488 29 28 32. E-mail address: sivarama@imec.be (H. Sivaramakrishnan Radhakrishnan).
URI: http://hdl.handle.net/1942/18812
DOI: 10.1016/j.solmat.2014.10.049
ISI #: 000351976000017
ISSN: 0927-0248
Category: A1
Type: Journal Contribution
Validation: ecoom, 2016
Appears in Collections: Research publications

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