Monte Carlo Calculations Pertaining to the Transport of Hot Electrons in Metals

Stuart, Rhona; Wooten, F.; Spicer, W. E.

doi:10.1103/physrev.135.a495

Cited by 90 publications

(27 citation statements)

References 10 publications

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“…The most successful approach uses internal photoemission, with which the attenuation length X a is determined from the metal-thickness dependence of the quantum yield in a metal-semiconductor photodiode [1]. A, , -can be estimated by modeling the process [2,3], which is complicated due to the dependence on photon energy of the energy distribution of the photoexcited carriers, whose spatial distribution is also dependent on the optical absorption in the film. A further shortcoming is the narrow kinetic energy (£kin) range, limited by the band gap of the semiconductor, over which X a can be measured.…”

Section: Hot Electron Scattering Processes In Metal Films and At Metamentioning

confidence: 99%

Hot electron scattering processes in metal films and at metal-semiconductor interfaces

Ludeke

Bauer

1993

Phys. Rev. Lett.

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Ballistic electron emission spectroscopy is used to investigate current attenuations in thin films of Pd/Si, from which the elastic and inelastic mean free paths are uniquely determined. The observed equality of transmission across Pd/Si(100) and Si(l 11) interfaces is attributed to interface scattering, on the basis of which a current transport model is developed that gives unprecedented agreement with experiment over a wide energy range.PACS numbers: 72.15.Lh, 73.50.Gr Hot electron scattering processes affect a variety of transport issues in metals and metal films, from current transfer ratios in metal-base transistors to escape depths in photoelectron and Auger electron spectroscopies. A common problem has been the determination of the elastic (X e ) and inelastic (A,,-) mean free paths (MFP) of the electrons in the metal from measured attenuation lengths. The most successful approach uses internal photoemission, with which the attenuation length X a is determined from the metal-thickness dependence of the quantum yield in a metal-semiconductor photodiode [1]. A, , -can be estimated by modeling the process [2,3], which is complicated due to the dependence on photon energy of the energy distribution of the photoexcited carriers, whose spatial distribution is also dependent on the optical absorption in the film. A further shortcoming is the narrow kinetic energy (£kin) range, limited by the band gap of the semiconductor, over which X a can be measured. These experimental as well as modeling complications are readily overcome by using ballistic electron emission microscopy (BEEM) on thin metal films deposited on semiconductors [4]. In BEEM, which is based on the scanning tunneling microscope (STM), nearly monochromatic electrons with energies determined by the basis Vj between the metal film and STM tip are injected and may traverse the layer to reach the metal-semiconductor (M-S) interface. If the electrons have sufficient energy to overcome the Schottky barrier eVo, they may cross the interface to be detected as a collector current I c in the semiconductor. X a can be obtained from the exponential decay of I c with film thickness, as previously reported for Au films on Si for £"kin~ 1 eV [5], Here we report I c attenuation studies of thin Pd films (8-90 A) on Si(lll) and Si (100) surfaces over an is kin range to 6 eV. For thicknesses ^ 40 A the attenuation curves become decidedly nonexponential with a shape that depends on E\^m. This behavior results from the interplay of two different scattering processes and affords a novel opportunity to extract their relevant MFP's. We present a simple model that treats the transport process from injection to collection as a random walk problem. From model fits to the attenuation data we uniquely determine the energy dependent X e (E) and Xt(E) in the 1-6 eV energy range.In addition, the nearly identical BEEM spectra for Pd on SiC111) and Si(100) for thickness w

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Section: Hot Electron Scattering Processes In Metal Films and At Metamentioning

confidence: 99%

Hot electron scattering processes in metal films and at metal-semiconductor interfaces

Ludeke

Bauer

1993

Phys. Rev. Lett.

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“…The barrier height is related to the work function (W) of the metal and the electron affinity (/) of the insulator, so the variation of materials selected for photodetection in the specific band leads to quite unique optical (especially electrical) response, which has to be carefully addressed in the design of the hot-electron photodetection system; for Ag, W Ag ¼ 4.26 eV 28 and for TiO 2 , / TiO2 ¼ 3.9 eV, 29 so the barrier energy U b ¼ 0.36 eV (i.e., k $ 3444 nm), which enables the concerned infrared photodetection. There are many models that describe this quantum process, [30][31][32][33] among which the most widely adopted is the WKB approximation that assumes the transmission probability is close to 100% when the electron energy (E ph ) > U b , otherwise the probability is close to zero. However, this model is too simplified without considering many other physical processes like electron reflections between the interfaces of two different materials.…”

Section: Device and Methodsmentioning

confidence: 99%

Surface-plasmon enhanced photodetection at communication band based on hot electrons

Zhan

et al. 2015

Journal of Applied Physics

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Surface plasmons can squeeze light into a deep-subwavelength space and generate abundant hot electrons in the nearby metallic regions, enabling a new paradigm of photoconversion by the way of hot electron collection. Unlike the visible spectral range concerned in previous literatures, we focus on the communication band and design the infrared hot-electron photodetectors with plasmonic metal-insulator-metal configuration by using full-wave finite-element method. Titanium dioxide-silver Schottky interface is employed to boost the low-energy infrared photodetection. The photodetection sensitivity is strongly improved by enhancing the plasmonic excitation from a rationally engineered metallic grating, which enables a strong unidirectional photocurrent. With a five-step electrical simulation, the optimized device exhibits an unbiased responsivity of ∼0.1 mA/W and an ultra-narrow response band (FWHM = 4.66 meV), which promises to be a candidate as the compact photodetector operating in communication band.

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“…Hence, it is desirable to devise a mean for enhancing their external efficiencies ( ex η ). Different basic physical models have been constructed to describe the quantum efficiency of thin-film Schottky barrier detectors based on Fowler theory [10,11] and Monte Carlo method [12]. Other research groups, considering various physical phenomena, have extended these models to be applicable for more practical detectors [2,7].…”

Section: Introductionmentioning

confidence: 99%

Nonidealities and Dark Current in IR Photodetector Based on Silicide-Nanolayer Schottky Barrier Integrated Into a Si Microring Resonator

Zali

Moravvej-Farshi

2015

IEEE J. Quantum Electron.

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Using a Z-transfer model applicable to a microring resonator enhanced internal photoemission based photodetector (MRRE-IPE-PD); we develop a model for evaluating the effect of reflections in the MRR on the quantum efficiency (QE). Simulations show that a 5% increase in the reflection from an ideal case QE and MRR quality factor reduces by ~30%. We also show that further increase in the reflection can result in a dramatic decrease in QE and break the degenerate resonant frequency down into two frequencies. Taking the detuning condition in an MRR into account we extend an existing model suitable for the MRRE-IPE-PD. We evaluate the effect of this non-ideality on the PD QE. A detuning equal to FSR/3 reduces the QE to half of its value for an ideal case. Nonetheless, for a detuning equal to FSR/2 the QE of the ideal case is retained.We also evaluate the dependence of the quantum efficiency bandwidth product (QE×BW) on the MRR radius in undercritical, critical, and over-critical coupling conditions. Simulations reveal that the latter is the optimized condition wherein the QE×BW for a PD with 2-nm PtSi decreases from 32 to 30 GHz, when the radius is increased from 7 to 10 μm.

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Monte Carlo Calculations Pertaining to the Transport of Hot Electrons in Metals

Cited by 90 publications

References 10 publications

Hot electron scattering processes in metal films and at metal-semiconductor interfaces

Hot electron scattering processes in metal films and at metal-semiconductor interfaces

Surface-plasmon enhanced photodetection at communication band based on hot electrons

Nonidealities and Dark Current in IR Photodetector Based on Silicide-Nanolayer Schottky Barrier Integrated Into a Si Microring Resonator

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