A better understanding of terahertz emission from semiconductor surfaces with a phased-array effect

Mannan, Abdul; Inoue, Ryotaro; Murakami, Fumio; Serita, Kazunori; Murakami, Hironaru; Tonouchi, Masayoshi

doi:10.1063/5.0077054

Cited by 8 publications

(4 citation statements)

References 40 publications

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“…2a−c . Due to the large beam diameter with 30° incident angle in our experiment, a long-time duration THz pulse was observed due to the surface charge oscillation and phased-array effect 31 . In order to directly reflect the dynamic properties of the photocarriers at the surface, we focus on the electric field at maximum intensity in the first peaks of the THz emission spectrum 18 , as shown in the yellow area.…”

Section: Resultsmentioning

confidence: 83%

“…The polarity of the THz emission waveform implies that the direction of the surface band bending, and amplitude of the THz emission correspond to the intensity of the surface potential, which means that the surface potential of the sample at different positions can be compared and estimated. In our experiment, the resolution is limited due to the phased-array effect 31 and the capability of the THz detector. The resolution can be further improved by using a smaller beam spot with a more sensitive near-field detector such as TeraSpike.…”

Section: Discussionmentioning

confidence: 98%

“…8a . The samples were excited at 80 MHz using an 800-nm source at an incident angle of 30° 31 , and the THz emission was focused onto the spiral GaAs THz antenna with variable delays. The beam diameter was as large as 5 mm to observe strong THz emission signals from the Si surface.…”

Section: Methodsmentioning

confidence: 99%

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Rapid, noncontact, sensitive, and semiquantitative characterization of buffered hydrogen-fluoride-treated silicon wafer surfaces by terahertz emission spectroscopy

et al. 2022

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Advances in modern semiconductor integrated circuits have always demanded faster and more sensitive analytical methods on a large-scale wafer. The surface of wafers is fundamentally essential to start building circuits, and quantitative measures of the surface potential, defects, contamination, passivation quality, and uniformity are subject to inspection. The present study provides a new approach to access those by means of terahertz (THz) emission spectroscopy. Upon femtosecond laser illumination, THz radiation, which is sensitive to the surface electric fields of the wafer, is generated. Here, we systematically research the THz emission properties of silicon surfaces under different surface conditions, such as the initial surface with a native oxide layer, a fluorine-terminated surface, and a hydrogen-terminated surface. Meanwhile, a strong doping concentration dependence of the THz emission amplitude from the silicon surface has been revealed in different surface conditions, which implies a semiquantitative connection between the THz emission and the surface band bending with the surface dipoles. Laser-induced THz emission spectroscopy is a promising method for evaluating local surface properties on a wafer scale.

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Section: Resultsmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 98%

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Rapid, noncontact, sensitive, and semiquantitative characterization of buffered hydrogen-fluoride-treated silicon wafer surfaces by terahertz emission spectroscopy

et al. 2022

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“…The materials to be studied by the TES include not only semiconductors but also superconductors, ferroelectrics, spintronic materials, and a wide range of other materials [3][4][5]. Thus the carrier dynamics also includes a variety of ultrafast physical phenomena, and the observables by TES mainly discuss their time-domain waveforms rather than Fourier transform spectra [6,7]. So universal applications can not be reached without understanding physics in more detail over the broad dimensional range in the time-domain, which requires to development of theoretical methodology and simulators, presumably with the supercomputer.…”

Section: Introductionmentioning

confidence: 99%

How to use terahertz emission spectroscopy for wide bandgap semiconductor evaluation

Tonouchi

2023

Terahertz Emitters, Receivers, and Applications XIV

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The time-domain waveforms of terahertz (THz) emission spectroscopy (TES) can tell us the ultrafast nature of the material photoresponse, and TES is becoming an essential tool to explore the advanced material functionalities and disclose the dynamics of the photocarriers. However, universal applications can not be reached without understanding physics in more detail over the broad dimensional range in the time-domain. We have applied TES and LTEM to Si-based materials and devices and proven that one can estimate various parameters, such as surface potential, work function, impurity doping density, defects density in passivation layers, surface state density, and so on, semi-quantitatively and non-contactly by just observing the THz radiation. In the present work, we review the TES application to wide bandgap semiconductors.

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Enhanced luminescence efficiency in Eu-doped GaN superlattice structures revealed by terahertz emission spectroscopy

Murakami,

Takeo,

Mitchell

et al. 2023

Commun Mater

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Eu-doped Gallium nitride (GaN) is a promising candidate for GaN-based red light-emitting diodes, which are needed for future micro-display technologies. Introducing a superlattice structure comprised of alternating undoped and Eu-doped GaN layers has been observed to lead to an order-of-magnitude increase in output power; however, the underlying mechanism remains unknown. Here, we explore the optical and electrical properties of these superlattice structures utilizing terahertz emission spectroscopy. We find that ~0.1% Eu doping reduces the bandgap of GaN by ~40 meV and increases the index of refraction by ~20%, which would result in potential barriers and carrier confinement within a superlattice structure. To confirm the presence of these potential barriers, we explored the temperature dependence of the terahertz emission, which was used to estimate the barrier potentials. The result revealed that even a dilutely doped superlattice structure induces significant confinement for carriers, enhancing carrier recombination within the Eu-doped regions. Such an enhancement would improve the external quantum efficiency in the Eu-doped devices. We argue that the benefits of the superlattice structure are not limited to Eu-doped GaN, which provides a roadmap for enhanced optoelectronic functionalities in all rare-earth-doped semiconductor systems.

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A better understanding of terahertz emission from semiconductor surfaces with a phased-array effect

Cited by 8 publications

References 40 publications

Rapid, noncontact, sensitive, and semiquantitative characterization of buffered hydrogen-fluoride-treated silicon wafer surfaces by terahertz emission spectroscopy

Rapid, noncontact, sensitive, and semiquantitative characterization of buffered hydrogen-fluoride-treated silicon wafer surfaces by terahertz emission spectroscopy

How to use terahertz emission spectroscopy for wide bandgap semiconductor evaluation

Enhanced luminescence efficiency in Eu-doped GaN superlattice structures revealed by terahertz emission spectroscopy

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