<i>In situ</i> chemical and structural investigations of the oxidation of Ge(001) substrates by atomic oxygen

Molle, Alessandro; Bhuiyan, Md. Nurul Kabir; Tallarida, G.; Fanciulli, M.

doi:10.1063/1.2337543

Cited by 137 publications

(85 citation statements)

References 13 publications

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“…The same approach in Ge is not effective due to GeO desorption at the surface, which leads to unstable Ge oxide. 120,121 Still, if Ge oxidation is forced far away from the surface, some Is injection can be obtained. Actually, very recently, it was shown that O implantation in Ge followed by 650 C annealing induces the formation of embedded GeO 2 nanoclusters (5-10 nm in size) able to induce a large TED of B.…”

Section: Point Defect Engineering and Enhanced B Diffusionmentioning

confidence: 99%

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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B migration in Si and Ge matrices raised a vast attention because of its inﬂuence on the production of conﬁned, highly p-doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (a-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In a-Si in the 450-650 C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 x10^20 B/cm3. B migration in a-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of a-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identiﬁed with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 °C a large Is supersaturation. These aspects of B diffusion are presented and discus...

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Section: Point Defect Engineering and Enhanced B Diffusionmentioning

confidence: 99%

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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“…9,10 A broad range of solutions was considered, e.g. Ge controlled oxidation 6,11 and deposition of passivating interfacial layer ͑IL͒. 12 Recently, a study on ZrO 2 / GeO 2 stacks prepared by atomic oxygen-assisted MBD ͑Ref.…”

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confidence: 99%

Thermally induced permittivity enhancement in La-doped ZrO2 grown by atomic layer deposition on Ge(100)

Lamagna¹,

Wiemer²,

Baldovino³

et al. 2009

Applied Physics Letters

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La-doped ZrO2 thin films grown by O3-based atomic layer deposition directly on Ge(100) exhibit a dielectric constant of 29. Upon annealing in N2 at 400 °C, a high κ value >40 is extracted for film thickness below 15 nm. Compositional depth profiling allows to correlate this observation with a remarkable Ge interdiffusion from the substrate which is consistent with the stabilization of the tetragonal ZrO2 phase. Ge interaction with the oxide stack and the formation of a germanate-like interfacial region, which acts as an electrical passivation for the Ge surface, are also investigated.

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“…Several studies have described the oxidation conditions for formation of the various Ge suboxide states. 23,24 These results suggest that when Ge NWs are exposed to air, the native oxide of Ge will form the Ge 2 O 3 (Ge 3þ ) stoichiometry predominantly. This oxide state will leave the germanium surface with some dangling bonds that can trap carriers and promote their non-radiative recombination.…”

mentioning

confidence: 91%

“…This oxide state will leave the germanium surface with some dangling bonds that can trap carriers and promote their non-radiative recombination. Annealing of Ge in molecular oxygen is expected to promote the formation of an oxide with the Ge 4þ oxidation state (identified by a chemical shift De ¼ 3.5 6 0.1 eV with respect to the bulk contribution of the Ge 3d levels 24,40 ). If this oxidation reaction occurs primarily at the GeO x /Ge interface, rather than at the oxide surface, a reduced interface trap density should result, [19][20][21] leading to more radiative recombination of photoexcited carriers and stronger bandedge photoluminescence.…”

mentioning

confidence: 99%

“…[21][22][23] Obtaining higher oxidation states (e.g., Ge 4þ ) in the oxide layer requires breaking additional Ge-Ge bonds, the rate of which can be accelerated by thermal annealing. 20,24,25 Here, we have used annealing in O 2 at moderate temperatures to control the state of oxidation of the Ge NW surface and to correlate the surface oxide stoichiometry with defect passivation using PL.…”

mentioning

confidence: 99%

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