화학공학소재연구정보센터
Electrochemical and Solid State Letters, Vol.14, No.1, P1-P4, 2011
First-Principles Prediction of Optical Absorption Enhancement for Si Native Defect Clusters under Biaxial Strain
We use density-functional theory calculations to qualitatively explore the effects of fourfold-coordinated vacancy (V-4) and interstitial (I-4) clusters on optical absorption spectra in crystalline Si (c-Si) under selected conditions of biaxial strain (epsilon = -3, 0, and 3%). While both native defect clusters enhance c-Si absorption by redshifting the absorption edge, we observe additional enhancement from biaxial strain. Increased strain magnitude tends to increase the absorption enhancement effect, but the optimal sign of strain exhibits a complementary relationship: compressive strain most effectively enhances V-4 absorption, while tensile strain most effectively enhances I4 absorption. The absorption redshift as a function of strain correlates well with effective bandgap reduction, including the appearance of an intermediate band under certain conditions (epsilon = -3 and 0%) for V-4. Our results suggest that manipulation of native defect distributions and their strain fields can be used to engineer the Si absorption spectra. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3511714] All rights reserved.