Quantum-chemical simulation of electrically active complexes at silicon grain boundaries

Alexander K. Fedotov 1Anis Saad 2Alexander L. Pushkarchuk 1Alexander V. Mazanik 1Kuten A. Semen 1

1. Belarusian State University (BSU), F. Skaryna av. 4, Minsk 220050, Belarus
2. 2Al-Balqa Applied University, Salt, Jordan

Abstract

The electrical activity or inactivity of contaminant-related deep centers at silicon grain boundaries (GBs) is very often connected with contaminating O- and/or C-atoms. In this work we analyse the tendencies in atomic and electronic structure of O- or/and C-containing complexes when contaminants were incorporated into Si tilt GB either separately or simultaneously. In the study we used a MM and MO LCAO method in PM3 approximation.

We have studied GBs containing SiOm or SinC complexes where m and n were between 1 and 4. It was shown that only incorporation of O-atoms between Si-atoms can form electrically active complexes with “chain”-like or “ring”-like configurations for m = 1-2 and SiO3 or SiO4 configurations for m = 3-4. С-containing electrically active complexes consisted of Si2C, Si3C and Si4C configurations, depending on number n of C-atoms inserted into 5- or 7-fold interstitial positions at GB “core”. Both O- and C-containing electrically active complexes at GB “core” were donor-like giving energy levels that were shifted with increasing number of contaminating atoms from EC to EC – 0.6 eV for O-incorporation and from EC – 0.536 eV to EC – 0.043 eV for C-incorporation.

The 2nd stage of simulation consisted of incorporation of C-atoms into SiOm complexes. This resulted in formation of Si-O-C-Si chains and shifting of donor-like levels generated by SiOm configurations back to the bottom of conduction band EC with the increasing of number of incorporated C-atoms. Therefore, simultaneous incorporation of O- and C-atoms into GB “core” in some configurations of atoms can result in compensation of electrical activity of O-containing complexes in SiOm configurations at the GB “core”.

 

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium F, by Alexander K. Fedotov
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-16 16:56
Revised:   2009-06-07 00:44