Hydrogen molecules and platelets in germanium

There has been substantial interest in the behaviour of hydrogen in silicon over the last decade, often focused on the behaviour of the interstitial hydrogen molecule and {111} oriented platelets. Less is known about analogous hydrogen-related defects in germanium, but planar defects are known, and the molecule has possibly been observed recently by Raman scattering.We present preliminary results of first-principles calculations on both the H2H2 molecule and a range of platelet geometries in germanium. For comparison the molecule in GaAs and Si is also simulated. Energetics and vibrational modes of the defects are presented. Our calculations show the observed weak mode at 3834cm-1 in Ge is indeed consistent with the interstitial hydrogen molecule.