Ab-initio modeling of carbon and carbon–hydrogen defects in InAs

• Published in: Physica. B, Condensed matter Vol. 401; pp. 275 - 277
• Main Authors: Torres, V.J.B., Coutinho, J., Briddon, P.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2007
• Subjects: Carbon; Hydrogen; InAs; LVM; Modeling; LVM; Hydrogen; InAs; Modeling; Carbon
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2007.08.165

Carbon is a common acceptor in several III–V semicondutors. In InAs, carbon replaces arsenic atoms, and when exposed to hydrogen, Raman and infra-red (IR) spectra reveal carbon–hydrogen centers. We perform density functional-pseudopotential studies to identify the observed Raman and IR lines. We replace an arsenic atom by carbon in a 64 atom InAs supercell, and investigated the energetics of a variety of possible hydrogen positions. In the lowest total energy configuration, hydrogen sits on a bond center position (BC), between the carbon and its indium first nearest neighbor. When hydrogen sits on the anti-bonding position to the carbon site the total energy is 0.4 eV higher than the BC structure. Other configurations showed higher energies. The local vibrational modes (LVM) of substitutional carbon were calculated at 502 cm −1, with a downward 13C-isotope shift of 19 cm −1. This is in excellent agreement with experimental data, were the frequency and shift were measured at 530 and 19 cm −1, respectively. C–H related LVMs for the BC configuration were obtained at 2744.9 cm −1 (A 1 −), 502.2 cm −1 (E +) and 394.5 cm −1 (A 1 +), which agree well with the experimental data at 2686.6, 518.2 and 393.2 cm −1, respectively. When 13C replaces 12C, the calculated downward shifts are 7.5 (A 1 −), 15.7 (E +) and 13.7 cm −1 (A 1 +), matching well the experimental data 7.7, 15.4 and 13.5 cm −1, respectively. An additional unreported H-wag mode is predicted at 689 cm −1.