Extended X-ray absorption fine structure spectroscopy of selenium-hyperdoped silicon

Newman, Bonna; Ertekin, Elif; Sullivan, Joseph T.; Winkler, M.; Marcus, Matthew A.; Fakra, Sirine C.; Sher, Meng-Ju; Mazur, Eric; Grossman, Jeffrey C.; Buonassisi, Tonio

doi:10.1063/1.4824279

Cited by 29 publications

(27 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some groups have thoroughly investigated Si supersaturated with S or Se prepared by laser irradiation in SF 6 atmosphere or by ion implantation and subsequently pulsed laser melted (PLM). [8][9][10][11][12] An extended infrared photoresponse with high gain levels has been shown. 13,14 In previous works, we have deeply investigated Si supersaturated with Ti 15 or V, 16 and we reported the first solar cell device based on Ti supersaturated Si.…”

Section: 2mentioning

confidence: 99%

Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

García-Hemme

García-Hernansanz

Olea³

et al. 2014

Applied Physics Letters

View full text Add to dashboard Cite

We report room-temperature operation of 1 × 1 cm2 infrared photoconductive photodetectors based on silicon supersaturated with titanium. We have fabricated these Si-based infrared photodetectors devices by means of ion implantation followed by a pulsed laser melting process. A high sub-band gap responsivity of 34 mV W−1 has been obtained operating at the useful telecommunication applications wavelength of 1.55 μm (0.8 eV). The sub-band gap responsivity shows a cut-off frequency as high as 1.9 kHz. These Si-based devices exhibit a non-previous reported specific detectivity of 1.7 × 104 cm Hz1/2 W−1 at 660 Hz, under a 1.55 μm wavelength light. This work shows the potential of Ti supersaturated Si as a fully CMOS-compatible material for the infrared photodetection technology.

show abstract

Section: 2mentioning

confidence: 99%

Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

García-Hemme

García-Hernansanz

Olea³

et al. 2014

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…For each doping concentration, we substituted one silicon atom with a Se impurity and relaxed the atomic positions (so that atomic forces are <0.01 eV/Å) and supercell lattice vectors (so that all stress tensor components are <2 kbar). We chose the substitutional Se configuration, as our electronic structure calculations 23 as well as others 24 indicate the substitutional site to be the minimum energy defect configuration. The QMC results presented here are computed via fixed node diffusion Monte Carlo conducted with the QWalk code 25 , with trial wave functions constructed with a Slater-Jastrow form using SIESTA's DFT orbitals, variance-minimized Jastrow coefficients, and a time step of 0.01 au.…”

mentioning

confidence: 99%

“…The QMC energies are computed by averaging over twisted boundary conditions for all supercells. Defect formation energies for both DFT and QMC were computed using ∆E f = (E Se1:Sin + µ Si ) − (E Sin+1 + µ Se ), wherein each atom's chemical potential µ is determined by the quasiequilibrium of the doped silicon with SiSe 2 chains, which may be present as early stage precipitates 23 .…”

mentioning

confidence: 99%

Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin

et al. 2012

Self Cite

View full text Add to dashboard Cite

Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band gap absorption arises from direct defect-to-conduction band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.Of all the experimentally measurable physical properties of materials, the electronic conductivity exhibits the largest variation, spanning a factor of 10 31 from the best metals to the strongest insulators 1 . Over the last century, the puzzle of why some materials are conductors and others insulators, and the mechanisms underlying the transformation from one to the other, have been carefully scrutinized; yet even after such a vast body of research over such a long period, the subject remains the object of controversy. In 1956, Mott introduced a model for the insulator-to-metal transition (IMT) in doped semiconductors, in which long-ranged electron correlations are the driving force 2 . Hyperdoping (doping beyond the solubility limit) creates a new materials playground to explore defect-mediated IMTs in semiconductors. In this letter, we identify a defect-induced IMT in silicon hyperdoped with selenium concentrations exceeding 10 20 cm −3(compared to the equilibrium solubility limit 3 of about 10 16 cm −3 ) and we explore the detailed nature of the transition with both experiment and computation. We find that the IMT is largely driven by electron correlation and most resembles a classic impurity-driven Mott transition. Additionally, we find that the high density of Se present at the IMT yields direct optical transitions and an absorption coefficient in excellent agreement with the measured sub-band gap optical properties 4 .Hyperdoping is currently being used to engineer new materials with unique and exotic properties. Silicon hyperdoped with chalcogens exhibits strong sub-band gap absorption down to photon energies as low as 0.5 eV 5-11 , sparking substantial recent interest in applications such as infrared detection and intermediate band photovoltaics [5][6][7][8][9][10][11] . The successful fabrication of rectifying junctions 10 and photodiodes 11-13 using S and Se hyperdoped silicon appears to justify such interest. While isolated S and Se dopants are well-established deep double donors in silicon 3,14 , the enhanced optical properties of hyperdoped silicon (in which these chalcogenic impurities are present at much higher concentrations) are not y...

show abstract

“…The first large peak in the spectrum is indicative of the scattering signal from the first nearest neighbor (1NN) shell of atoms. 22 It can also be noted that the amplitudes of |v(R)| from higher-order shells (R > 2 Å ) for all other spectra are strongly attenuated, except for the spectrum collected at Zn K-edge for sample Z1T0 (pure ZnO). This suggests that the higher-order shells around the Zn atoms are well-ordered in the pure ZnO sample, verifying its crystalline nature.…”

mentioning

confidence: 99%

“…The energy scale is calibrated by using the absorption edge of reference metallic Zn or Sn thin films measured simultaneously and the XANES and EXAFS are isolated by normalizing the absorption spectrum and subtracting the smooth atomic background absorption signal from the measured absorption signal using the AUTOBK algorithm in Athena with R bkg ¼ 1.0 Å . 21,22 After the background removal, the processed data are transformed from energy space to k-space using the relationship,…”

mentioning

confidence: 99%

X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

Siah

Lee

et al. 2014

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

We investigate the correlation between the atomic structures of amorphous zinc-tin-oxide (a-ZTO) thin films grown by atomic layer deposition (ALD) and their electronic transport properties. We perform synchrotron-based X-ray absorption spectroscopy at the K-edges of Zn and Sn with varying [Zn]/[Sn] compositions in a-ZTO thin films. In extended X-ray absorption fine structure (EXAFS) measurements, signal attenuation from higher-order shells confirms the amorphous structure of a-ZTO thin films. Both quantitative EXAFS modeling and X-ray absorption near edge spectroscopy (XANES) reveal that structural disorder around Zn atoms increases with increasing [Sn]. Field-and Hall-effect mobilities are observed to decrease with increasing structural disorder around Zn atoms, suggesting that the degradation in electron mobility may be correlated with structural changes. V C 2014 AIP Publishing LLC. The high mobility and amorphous structure of AMOS enable a faster operation of the devices and elimination of grain-boundary related defects, respectively.2,3 The high electron mobility in the amorphous state originates from the conduction band, which mainly consists of unoccupied Ns (N ! 5) orbitals of metal atoms such as In-5s in a-IGZO. [4][5][6] The spherical symmetry of the s orbitals makes them less prone to form traps and scattering centers when the metal-oxygen-metal bonds are distorted by rotation of metal-oxygen polyhedrons.Amorphous zinc-tin-oxide (a-ZTO) is recently highlighted as a promising candidate material for cost-effective applications, as it is free from toxic and expensive elements (e.g., indium and gallium). Sn] ratio in a-ZTO thin films on device performance suggests a strong correlation between the atomic structure and electronic transport properties of the films. Because amorphous materials can exhibit a continuum of structures, 18 a probe of local order is needed. In this work, we investigate the effect of atomic structure in a-ZTO on electron transport properties by using synchrotron-based X-ray absorption spectroscopy (XAS). We perform EXAFS at the Zn and Sn K-edges to probe the local chemical neighborhoods of Zn and Sn atoms in a-ZTO films, respectively. We find that the Debye-Waller factor, which gives a measure of structural disorder, 19 at the Zn K-edge increases with increasing [Sn] in the films. The structural disorder is further investigated by XANES analysis, which indicates the amorphization around Zn atoms with increasing [Sn] in the films. Disorder as measured by EXAFS and XANES coincides with a decrease in measured electron mobility, suggesting that the degradation in electron mobility may be correlated with structural changes for Zn rich films ([Zn] > 0.5), whereas for Sn rich regions, larger ionic size of Sn dominates the electron mobility.A set of a-ZTO thin films is grown on quartz substrates by ALD at a growth temperature of 120 C. Diethylzinc (DEZ) and a cyclic tin (II) amide ((1,3-bis(1,1-dimethylethyl)-4,5-dimethyl-(4R,5R)-1,3,2-diazastannolidin-2-ylidene)Sn(II)) 20 are used as th...

show abstract

Extended X-ray absorption fine structure spectroscopy of selenium-hyperdoped silicon

Cited by 29 publications

References 39 publications

Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin

X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

Contact Info

Product

Resources

About