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Polycrystalline silicon thin films for photovoltaics

Citation

Chen, Claudine M. (2001) Polycrystalline silicon thin films for photovoltaics. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:12162010-081444511

Abstract

Selective nucleation and solid phase epitaxy offers a low temperature method to fabricate large grain, polycrystalline silicon on foreign substrates. Undoped and highly doped silicon films were nucleated with nickel or indium and annealed at 600°C. Indium nucleated crystallization proceeded by conventional solid phase epitaxy. Undoped silicon had grain sizes of 1-2 µm. With doping, although there was enhancement of the growth rate, the grain size did not increase, since the incubation time correspondingly decreased. The exception was the phosphorus-doped silicon that had a maximum grain size of 10 µm. In nickel-nucleated samples, the amorphous silicon layer fully crystallized before the onset of random nucleation, achieving grain sizes on order of tens of microns. Within each grain, however, were many low angle, sub-grain boundaries that came from the needle-like crystal growth. Epitaxy on these layers resulted in strained columnar crystals with dislocations. Positron annihilation spectroscopy (PAS) was used to study vacancies in solid phase crystallized silicon in four doping cases: undoped, B-doped, P-doped, and P and B-doped. Oxygen-vacancy complexes were seen in all samples and phosphorus-vacancy complexes in the P- and P and B-doped samples. Progressive etchback of a subset of the samples was achieved, and a defect concentration on order of 10^(15) cm^(-3) was estimated for all samples.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Physics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Atwater, Harry Albert
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 June 2001
Record Number:CaltechTHESIS:12162010-081444511
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:12162010-081444511
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6209
Collection:CaltechTHESIS
Deposited By: Rita Suarez
Deposited On:16 Dec 2010 18:25
Last Modified:26 Dec 2012 04:32

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