Local Vibrational Modes of Isolated Hydrogen in Germanium

Abstract

Two distinct isolated hydrogen defects are observed in crystalline Ge by in situ infrared absorption spectroscopy. Implantation of protons into Ge at cryogenic temperatures gives rise to two intense absorption lines at 745 and 1794 cm(-1). The lines originate from distinct defects, each of which contains one H atom located on a <111> axis. The 1794-cm(-1) line is assigned to bond center H in the positive charge state, whereas the 745-cm(-1) line is ascribed to negatively charged H located on a <111> axis close to the tetrahedral site.

Laser CVD of Nanodisperse Ge–Sn Alloys Obtained by Dielectric Breakdown of SnH4/GeH4 Mixtures

“…[Although this species has not yet been detected for Sn and Ge/Sn, it is infrared active in Ge at 700 and 1880 cm -1 (ref. [29] ) and Raman active at 745, 1794 and 3630 cm -1 (refs. [29,30] )].…”

Effect of local electron-electron correlation in hydrogen-like impurities in Ge

“…1 obtained with the FPLO code, 45 the bands with predominantly H 1s character can be readily identified. In both the HGe 8 and HGe 64 supercells, the H 1s local density of states (DOS) bifurcates into two peaks, one in and just below the gap and the other around −5 eV. Whereas these peaks are effectively separate in the larger cell, they form the boundaries of a broad but bifurcated 1s bandwidth of bandwidth W ≈ 5-6 eV.…”

“…Choosing two different supercell sizes allows us to further study the influence of effective H-Ge hybridization beyond simply reducing the hopping matrix elements and tests to what degree the influence of the H impurity is spatially localized. There is vibrational evidence 8,9 that H sits off the tetrahedral site along a [111] direction, thus closer to one of the four Ge ions than the others, giving it only one Ge nearest neighbor. We do not treat that possibility here, although the methods we use can be applied to that case.…”

“…In fact, it appears to be split across two bands, frustrating attempts to isolate and manipulate it. Naturally, excluding the Ge sp screening increases the resulting value of the H 1s Hubbard U , which can be considered as an upper limit, and so the value of U most appropriate for our HGe 8 DMFT calculations (in which we only treat the dynamical correlations on the H 1s orbital) is likely smaller than the 11.2 eV we report in Table I. Due to the difference in correlated subspaces considered and the many varied parameters in the DMFT treatment, it is most appropriate to view this cRPA analysis as a separate method for understanding the H impurities and as a way to check FIG.…”

“…Several H-related defects have been observed [3][4][5][6][7] in Ge, and most seem to be defect complexes in which H is involved, rather than simply isolated H impurities. However, local vibrations were observed for isolated H, identified as (near) bond-centered and in the antibonding or tetrahedral sites, 8,9 which is the impurity of interest here. Similar questions exist for H impurities in the isovalent semiconductors Si 10 and diamond.…”