Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon

Stolk, P. A.; Saris, F.W.; Berntsen, A. J. M.; Weg, W. F. van der; Sealy, L.; Barklie, R.C.; Krötz, G.; Müller, Gerhard

doi:10.1063/1.356662

Cited by 71 publications

(64 citation statements)

References 90 publications

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“…On the other hand, the transient diffusion is related to two distinct causes for db density reduction. The first one is the db-fb annihilation (whose rate is in agreement with literature data 20 ), which quickly reduces the B diffusivity in the early stages of annealing. The second cause is the progressive reduction of db density due to db diffusion itself.…”

Section: Defect Assisted B Diffusionsupporting

confidence: 75%

“…%, in agreement to literature data. 20,23,42 c resulted to be 1.0 6 0.5, confirming that one excess db is generated by one un-clustered B atom in amorphized Si. n c was found to be temperature independent, with a value of about 2.2 Â 10 20 B/cm 3 , again in full agreement with literature indications.…”

Section: Defect Assisted B Diffusionmentioning

confidence: 50%

“…20,27 Such a process was shown to be reversible, even if with an hysteresis loop, since ion implantation (leading to a damage level larger than $0.1 displacements per atom) performed on relaxed a-Si reproduces the same strain status as in the asimplanted a-Si. 20,27 High resolution investigation of the radial distribution function of a-Si also showed that the coordination number in the first neighbor atomic shell increases from 3.79 to 3.88 going from the as-implanted to the relaxed state, compatible with the removal of coordination defects during the structural relaxation. 28 This undercoordination in a-Si with respect to four-fold coordinated c-Si was furthermore related to the slightly lower atomic density in a-Si (about 2%) than in c-Si.…”

Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 93%

“…Still, at all temperatures, the observed diffusivity transient is much longer (10 to 100 times) than the a-Si relaxation times reported in literature. 20 Given these experimental features for B diffusion in a-Si, a simple formula for D B as a function of the concentration cannot account for the complex aspects of the phenomenon. In summary, the B migration in a-Si: (i) has a transient character, which cannot be explained only with the wellknown relaxation of a-Si; (ii) has a non-trivial concentration dependence, which determines a larger diffusivity, the greater the global amount of B in the surroundings is.…”

Section: B Main Features Of B Migrationmentioning

confidence: 99%

“…The lack of the longrange order (distinctive of the crystalline state) is caused by a quite broad distribution of the Si-Si bong angle (diverging up to 12 from the crystalline value of 109.47 ), which leads in the a-Si structure to five-and seven-membered atoms rings in addition to the six-membered atoms rings typical of the diamond lattice. 20,21 The large distribution in the bond angle is due, on one hand, to the distortion of the four-fold coordinated Si atoms from the lattice position and, on the other hand, to the presence of a great amount of coordination defects of a-Si, namely the dangling bond (db, a three-fold coordinated Si atom) and the floating bond (fb, a five-fold coordinated Si atom). [22][23][24][25] Both the coordination defects and the bond angle distortion depend on the process history of a-Si, since it was widely shown that as-implanted a-Si, if annealed, undergoes a structural relaxation, with a heat release measured by differential scanning calorimetry at temperatures below the onset of crystallization.…”

Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 99%

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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: Defect Assisted B Diffusionsupporting

confidence: 75%

Section: Defect Assisted B Diffusionmentioning

confidence: 50%

Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 93%

Section: B Main Features Of B Migrationmentioning

confidence: 99%

Section: A Defects and Diffusion In Amorphous Simentioning

confidence: 99%

See 3 more Smart Citations

Mechanisms of boron diffusion in silicon and germanium

Mirabella

Salvador

Napolitani

et al. 2013

Journal of Applied Physics

103

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Thermal Properties and Heat Transport in Silicon‐Based Nanostructures

Chang

Tsybeskov

2010

Silicon Nanocrystals

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IntroductionFor the past 40 years, crystalline Si (c-Si) continues to be the major material for microelectronics, and modern silicon technology is superior compared to other semiconductors (e.g., II-VI and III-V compounds). In addition to the unique electronic and structural properties of bulk c-Si, silicon dioxide (SiO 2 ) and Si/SiO 2 interfaces, single-crystal Si possesses one of the best known lattice thermal conductivity [1,2]. This exceptional heat conductance is critically important for Si device heat management and circuit reliability. However, most of the modern complementary metal-oxide-semiconductor (CMOS) platforms are no longer single-crystal Si wafers but rather thin layers of Si-on-insulator (SOI), ultrathin strained Si and SiGe heterostructures that are the foundation of SiGe bipolar transistors (HBTs), and high-mobility metal-oxide-semiconductor field-effective transistors (MOSFETs). Major properties of these Si-based nanostructures are very different from those of bulk c-Si. For example, thermal conductivity in ultrathin SOI layers, SiGe alloys, and Si/SiGe nanostructures could be reduced by more than an order of magnitude compared to that in c-Si [3-6], and heat dissipation has become an important issue for modern nanoscale electronic devices and circuits. Thus, the understanding and improvement of heat management in Si-based nanostructures is critically important for the evolution of microelectronic industry.On the other hand, many interesting applications of nanostructured Si (ns-Si) in photonic devices and CMOS-compatible light emitters were recently discussed [7][8][9][10][11]. These ns-Si materials and devices can be produced by electrochemical anodization (i.e., porous Si [12]), chemical vapor deposition (CVD) using thermal decomposition of SiH 4 [13-15], Si ion implantation into a SiO 2 matrix [16], and deposition of amorphous Si/SiO 2 layers followed by thermal crystallization [17][18][19]. These ns-Si materials and devices produce an efficient and tunable light emission in the near-infrared and visible spectral region [20,21]. Also, it has been shown that under photoexcitation with energy density >10 mJ/cm 2 , optical gain is possibly Silicon Nanocrystals: Fundamentals, Synthesis and Applications. Edited by Lorenzo Pavesi and Rasit Turan

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Investigating subsurface damages in semiconductor–insulator–semiconductor solar cells with THz spectroscopy

Blumröder

Hempel

Füchsel

et al. 2016

Physica Status Solidi (a)

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The influence of near-surface crystal damage on carrier dynamics in silicon has been investigated with optical-pump THz-probe and THz emission studies. The surface damage is caused by a plasma process used for the fabrication of the ultrathin insulator within semiconductor-insulator-semiconductor (SIS) solar cells. The ion bombardment during the plasma process introduces a highly damaged subsurface region. Furthermore, the integration of positive interface charges leads to the formation of a depletion region that can be detected via the emitted THz radiation. The results are compared with classic I-U-characterization demonstrating that THz spectroscopy can be used as a supplementary tool for the investigation of process-induced surface damages

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Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon

Abstract: Articles you may be interested inComparative analysis of electronic structure and optical properties of crystalline and amorphous silicon nitrides

Cited by 71 publications

References 90 publications

Mechanisms of boron diffusion in silicon and germanium

Mechanisms of boron diffusion in silicon and germanium

Thermal Properties and Heat Transport in Silicon‐Based Nanostructures

Investigating subsurface damages in semiconductor–insulator–semiconductor solar cells with THz spectroscopy

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