Local modes of hydrogen defects in Si:Ge and Ge:Si

• Published in: Physica. B, Condensed matter Vol. 376; pp. 22 - 27
• Main Authors: Pereira, R.N., Bech Nielsen, B., Coutinho, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2006
• Subjects: Ab initio theory; FTIR; Hydrogen; SiGe; SiGe; Hydrogen; FTIR; Ab initio theory
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2005.12.008

We give an overview of the results obtained from joint experimental and theoretical studies of H in Si-rich (Si:Ge) and Ge-rich (Ge:Si) SiGe. Si:Ge and Ge:Si implanted at low temperatures with H + and/or D + have been studied by in situ infrared absorption spectroscopy. The states of isolated H and H dimers in dilute SiGe have also been investigated by ab initio theory. Four configurations of positively charged bond-centered H ( H BC + ) have been identified both in Si:Ge and in Ge:Si. Interestingly, the infrared spectrum arising from H BC + centers in Ge:Si is a mirror image of that observed for Si:Ge, which is a direct result of the opposite sign of the strain field induced by Si–Ge bonds on the lattice of Si:Ge and Ge:Si materials. We found that, unlike Ge in Si:Ge, the Si atoms in Ge:Si are efficient trapping sites for H, resulting in the appearance of H anti-bonded to Si at low temperatures and H dimers in the form of Ge – H BC ⋯ Si – H AB defects at room temperature.