Vibrational properties of elemental hydrogen centres in Si, Ge and dilute SiGe alloys

Abstract

The local vibrational modes arising from single interstitial hydrogen centres in Si, Si-rich SiGe, Ge-rich SiGe, and Ge crystals are modelled by an ab initio supercell method. The stress response of the 1998 and 1794 cm −1 bands that appear in proton-implanted Si and Ge samples is well reproduced, further confirming their assignment to bond-centred H + defects. It is shown that H − in Ge is anti-bonded to a Ge atom, and is likely to be considerably less mobile than in Si. Although H + is not trapped by the minority species in both Si-rich and Ge-rich alloys, we find that H − can be stabilized by forming anti-bonded H-Si structures.

Antibonding configurations of hydrogen in silicon-germanium alloys

“…%͒ have recently been calculated by the density-functional supercell method. 35 The authors find that in Ge 1−x Si x negatively charged hydrogen is stabilized in antibonding sites attached silicon atoms, which is the energetically favorable configuration for negatively charged hydrogen in Ge-rich SiGe. This finding fully agrees with the annealing behavior of the lines ascribed to the H AB − ͑Si͒ and H AB − ͑Ge͒ defects.…”

“…35 The authors predict that negatively charged hydrogen in Ge-rich SiGe may be stabilized at antibonding ͑AB͒ sites attached to a silicon atom. This defect corresponds to hydrogen located at the AB1 site shown in Fig.…”

“…A fairly detailed understanding of the behavior of isolated hydrogen in pure Si and in pure Ge has been achieved from intense experimental [14][15][16][17][18][19][20][21][22][23][24] and theoretical [25][26][27][28][29][30][31][32][33][34][35] research. Isolated hydrogen atoms are known to exist in Si and in Ge in three different charge states H + , H 0 , and H − , whose occurrences depend on the doping type.…”

Muonium hyperfine parameters in Si1−xGex alloys

“…Studies of impurity behaviour in the bulk alloy, particularly those which span the composition range, are quite limited, however. With regard to hydrogen, infrared absorption [6] and DLTS [7] studies have focused on observations of bond-centred hydrogen properties in dilute alloys at either end of the composition range; theoretical studies have enabled local vibrational modes of this species to be modelled for similar compositions [8]. In these cases, modified properties of the bond-centred species have been observed owing to altered local bonding environments due to the presence of near-by impurity atoms.…”