Muonium defect states and ionization energies in SiGe alloys

King, P.J.C.; Lichti, R.L.; Carroll, B.R.; Celebi, Y.G.; Chow, K. H.; Yonenaga, Ichiro

doi:10.1016/j.physb.2007.09.035

Cited by 10 publications

(5 citation statements)

References 16 publications

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“…The most convincing support for this interpretation comes from the Si 1−x Ge x alloys, where the muonium acceptor level is seen in more direct measurements to approach the valence band edge with increasing Ge content, crossing it at x ≈ 0.9 (King et al 2007). This is shown in figure 16(a).…”

Section: Germaniummentioning

confidence: 78%

“…The relation with the quasi-atomic normal muonium would need elucidating-notably the fact that Mu 0 T reappears as a transient state at high temperature, dominating the chargeexchange relaxation under conditions close to thermodynamic equilibrium. The neutral shallow acceptor would presumably have a very low hyperfine splitting and ionization temperature, et al (1999a) and King et al (2007) in (a) suggest an acceptor level approaching the valence band maximum with increasing Ge content, becoming band-resonant in the pure element. Donor and acceptor levels determined for muonium in GaAs, Ge and Si by Lichti et al (2008) are plotted in (b) on the band-offset diagram used by Van de Walle and Neugebauer (2003) in their prediction of a universal H(+/−) alignment at the charge neutrality level.…”

Section: Germaniummentioning

confidence: 97%

“…We must use the term hydrogen-like if we want to describe compact hydrogen defect centres. 13 The muonium studies are particularly pertinent to SiGe production by chemical vapour deposition (CVD), where hydrogen cannot be excluded: see measurements by King et al (2003King et al ( , 2005King et al ( , 2007 and calculations by Hourahine et al (2003), Pereira et al (2006). For pure Si, the low-temperature yields of Mu and Mu * per implanted muon are 61% and 37%, respectively, 72% and 8% for pure Ge (see Patterson (1988), who also gives the evolution of amplitudes and linewidths with temperature-his figure 67 for Si, 74 for Ge).…”

Section: Metastability: Cage-centred and Bond-centred Muoniummentioning

confidence: 99%

“…Mu 0 T is depolarized by encounter with unionized dopants below 12 K, with hop rates estimated as 10 14 s −1 , or over 10 8 per muon lifetime (Weidinger et al 1981). A degree of disorder appears to stabilize the BC site, presumably by provision of strained or pre-stretched bonds: the amorphous material a-Ge : H shows a robust repolarization and resonance signature of Mu 0 BC up to 200 K at least (Mytilineou et al 1998b), while for certain compositions of SiGe alloy its TF precession signal is visible almost to room temperature (King et al 2007).…”

Section: Germaniummentioning

confidence: 99%

“…Muonium acceptor levels in SiGe alloys (a), donor and acceptor levels in selected materials(b). The combined data ofLichti et al (1999a) andKing et al (2007) in (a) suggest an acceptor level approaching the valence band maximum with increasing Ge content, becoming band-resonant in the pure element. Donor and acceptor levels determined for muonium in GaAs, Ge and Si byLichti et al (2008) are plotted in (b) on the band-offset diagram used byVan de Walle and Neugebauer (2003) in their prediction of a universal H(+/−) alignment at the charge neutrality level.…”

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confidence: 99%

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Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

2009

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Although the interstitial hydrogen atom would seem to be one of the simplest defect centres in any lattice, its solid state chemistry is in fact unknown in many materials, not least amongst the elements. In semiconductors, the realization that hydrogen can profoundly influence electronic properties even as a trace impurity has prompted its study by all available means-but still only in the functionally important or potentially important materials-for the elements, Si, Ge and diamond. Even here, it was not studies of hydrogen itself but of its pseudo-isotope, muonium, that first provided the much needed microscopic pictures of crystallographic site and local electronic structure-now comprehensively confirmed by ab initio computation and such data as exists for monatomic, interstitial hydrogen centres in Si. Muonium can be formed in a variety of neutral paramagnetic states when positive muons are implanted into non-metals. The simple trapped atom is commonly only metastable. It coexists with or reacts to give defect centres with the unpaired electron in somewhat more extended orbitals. Indications of complete delocalization into effective mass states are discussed for B, α-Sn, Bi and even Ge, but otherwise all the muonium centres seen in the elemental semiconductors are deep and relatively compact. These are revealed, distinguished and characterized by µSR spectroscopy-muon spin rotation and resonance informing on sites and spin-density distributions, muon spin relaxation on motional dynamics and charge-state transitions.This Report documents the progress of µSR studies for all the semiconductors and semimetals of the p-block elements, Groups III-VI of the Periodic Table . The striking spectra and originally unanticipated results for Group IV are for the most part well known but deserve summarizing and updating; the sheer diversity of muonium states found is still remarkable, especially in carbon allotropes. The interplay of crystallographic site and charge state in Si and Ge at high temperatures, or under illumination, reflects the capture and loss of charge carriers that should model the electrical activity of monatomic hydrogen but still challenges theoretical descriptions. Spin-flip scattering of conduction electrons by the paramagnetic centres is revealed in heavily doped n-type material, as well as some modification of the local electronic structures. The corresponding spectroscopy for the solid elements of Groups III, V and VI is rather less well known and is reviewed here for the first time; a good deal of previously unpublished data is also included. Theoretical expectations and computational modelling are sparse, here. Recent results for B suggest a relatively shallow centre with molecular character; P and As show deeper quasi-atomic states, but still with substantial overlap of spin density onto surrounding host atoms. Particular attention is paid to the chalcogens. Muonium centres in Te show charge-state transitions already around room temperature; the identification of those in S and Se has been compli...

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Section: Germaniummentioning

confidence: 78%