Hydrogen molecules in semiconductors

Abstract

Molecular hydrogen, the simplest of all molecules, allows a direct insight into the fundamental properties of quantum mechanics. In the case of H 2, the Pauli principle leads to two different species, para-H 2 and ortho-H 2. A conversion between these species is prohibited. Vibrational mode spectra reflect the fundamental properties and allow an unambiguous identification of the H 2 molecules. Today, we have experimental evidence for the trapping of hydrogen molecules in the semiconductors Si, Ge and GaAs at the interstitial sites, within hydrogen-induced platelets, in voids and at impurities (interstitial oxygen in Si). Interstitial H 2 is a nearly free rotor with a surprisingly simple behavior. We review on interstitial H 2 in semiconductors and report on the unexpected preferential disappearance of the para-H 2 or ortho-D 2 species. The origin of the detected ortho– para conversion will be discussed.