Effects of compressive stress on the electronic states and atomic configurations of the Pt–H 2 defect in silicon

Abstract

We review our recent results and analyses of the effects of uniaxial compressive stress on the electronic states and atomic configurations of a platinum–dihydrogen (Pt–H 2) defect in Si, and discuss the results on the basis of the structural model that we proposed. We applied a technique of isothermal deep-level transient spectroscopy (IT-DLTS), combined with the application of uniaxial compressive stress. Our experiments showed that 〈1 1 1〉 and 〈1 0 0〉 stresses split the IT-DLTS peak of the Pt–H 2 defect into two components, and a 〈1 1 0〉 stress split it into three components. Such a splitting pattern and the observed intensity ratios of split components uniquely determined that the defect had C 2v symmetry, on which our structural model was based. We found that the electronic levels corresponding to split components varied linearly with 〈1 1 1〉 stress. Subtracting the stress shift of the conduction band minima, we have obtained 36 ± 4 meV/GPa as a net increase in energy for the level with the higher energy with respect to the applied stress. This result strongly suggests that compressive stress raises the energy of the Pt–H 2 level, indicating its antibonding character. We observed that the Pt–H 2 defect was aligned above 80 K under uniaxial stress to the configuration with the higher electronic level. This indicates that the stress-induced increase of level energy was overcome by the energy gain due to electronic bonding and atomic relaxation, resulting in the decrease of the total energy of the Pt–H 2 defect system. We found that the intensity ratio of split components of the IT-DLTS peak was described by a Boltzmann factor, where the activation energy is proportional to the magnitude of the applied stress up to 0.4 GPa with a proportional factor, 49 meV/GPa, from which we determined an element A 3 of the piezospectroscopic tensor to be −37 meV/GPa.