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Title:
 
Lattice Positions and Electronic Properties of Titanium in Silicon
 
Author(s):
 
A.G. Marinopoulos, J. Coutinho, V.P. Markevich, S. Leonard, A.R. Peaker, B. Hamilton
 
Keywords:
 
Silicon (Si), Solar Cell, Impurities, Density Functional Theory, deep level transient spectroscopy
 
Topic:
 
WAFER-BASED SILICON SOLAR CELLS AND MATERIALS TECHNOLOGY
Subtopic: Silicon Feedstock, Crystallisation and Wafering
Event: 29th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AV.1.55
 
Pages:
 
804 - 808
ISBN: 3-936338-34-5
Paper DOI: 10.4229/EUPVSEC20142014-2AV.1.55
 
Price:
 
 
0,00 EUR
 
Document(s): paper
 

Abstract/Summary:


The electronic structure and electrical levels of Ti impurities in Si were studied theoretically and experimentally. We performed calculations based on density-functional theory with an explicit treatment of correlation among the 3d electrons of Ti. Our experiments included secondary ion mass spectroscopy (SIMS) and deep level transient spectroscopy measurements on Czochralski (Cz)- and float-zone-grown (FZ) Si implanted with Ti ions and annealed in the temperature range 600-900°C. Our calculations agree with earlier results concerning the electrical levels of Ti occupying interstitial positions (Tii). Nonetheless, we find that substitutional Ti (Tis) does not induce levels inside the gap (as previously thought) and that the intra-atomic correlation leads to electrically inert Tis. Experimentally the electrical behavior of Ti atoms is found to be different in Cz- and FZ-Si annealed at 650°C although the Ti SIMS profiles are similar. We argue that Tii atoms in FZ-Si react with the much more numerous vacancies and become substitutional. No levels which could be assigned to Tis were detected, confirming the present calculations. The differences between FZ- and Cz-Si are also explained from the calculations which predict a stronger binding of Tii to vacancies than to interstitial oxygen atoms (which are abundant in Cz-material).