Probing the surface potential of oxidized silicon by assessing terahertz emission

Mochizuki, Takayasu; Ito, Akihiro; Mitchell, J.; Nakanishi, Hachiro; Tanahashi, Katsuto; Kawayama, Iwao; Tonouchi, Masayoshi; Shirasawa, Katsuhiko; Takato, Hidetaka

doi:10.1063/1.4980847

Cited by 32 publications

(19 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently we have applied the TES to the various semiconductors. Examples are the evaluation of the surface potential of the passivated Si wafers, 15,16 which would bring the TES into the real semiconductor industrial applications, the study on the conduction band bending of the -Ga2O3 near the surface with TES for the first time, 17 and the imaging of the spontaneous polarization in GaN. 18 The ultrafast optical response in the wide bandgap semiconductors is still an unexplored area where it is worth applying TES.…”

Section: Introductionmentioning

confidence: 99%

Simplified formulas for the generation of terahertz waves from semiconductor surfaces excited with a femtosecond laser

Tonouchi

2020

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

We derive simple formulas to explain terahertz (THz) emission from semiconductor surfaces excited by a femtosecond (fs) laser. Femtosecond optical pulses with energies larger than the bandgap create photocarriers which travel and generate THz radiation, according to the time derivative of the photocurrent. By assuming that only electrons traveling in an ultrafast time scale, less than a few hundred fs, contribute to THz radiation, one can obtain simple expressions for the emission originating from the photocarrier drift accelerated with a built-in field or from the photocarrier diffusion. The emission amplitude of the former is in proportion with electron mobility, the Schottky-Barrier height, and the laser intensity and one of the latter with the laser intensity and diffusion coefficient squared. We also discuss the formula for emission from metal-insulator-semiconductor structures. The derived expressions are useful in understanding the THz emission properties observed by a laser THz emission microscope (LTEM), bringing LTEM into real applications in the field of semiconductor research and development.

show abstract

Section: Introductionmentioning

confidence: 99%

Simplified formulas for the generation of terahertz waves from semiconductor surfaces excited with a femtosecond laser

Tonouchi

2020

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…The dynamics-related information provided is different from that provided by typical photoluminescence, electroluminescence, and laser-induced photocurrent characterization methods [6]. We have reported several examples in which defect analysis [7], noncontact surface potential estimation [8,9], and nondestructive evaluation of solar cells [10] are demonstrated and shown that TES and LTEM are practical tools for semiconductor research and development. In the present study, we employ TES and LTEM to study local ultrafast photocarrier dynamics in β-Ga 2 O 3 , which has an ultrawide bandgap of approximately 4.7-4.9 eV [3,[11][12][13].…”

Section: Introductionmentioning

confidence: 94%

Terahertz Emission Spectroscopy and Microscopy on Ultrawide Bandgap Semiconductor β-Ga2O3

et al. 2020

Self Cite

View full text Add to dashboard Cite

Although gallium oxide Ga2O3 is attracting much attention as a next-generation ultrawide bandgap semiconductor for various applications, it needs further optical characterization to support its use in higher-performance devices. In the present study, terahertz (THz) emission spectroscopy (TES) and laser THz emission microscopy (LTEM) are applied to Sn-doped, unintentionally doped, and Fe-doped β-Ga2O3 wafers. Femtosecond (fs) laser illumination generated THz waves based on the time derivative of the photocurrent. TES probes the motion of ultrafast photocarriers that are excited into a conduction band, and LTEM visualizes their local spatiotemporal movement at a spatial and temporal resolution of laser beam diameter and a few hundred fs. In contrast, one observes neither photoluminescence nor distinguishable optical absorption for a band-to-band transition for Ga2O3. TES/LTEM thus provides complementary information on, for example, the local mobility, surface potential, defects, band bending, and anisotropic photo-response in a noncontact, nondestructive manner. The results indicated that the band bends downward at the surface of an Fe-doped wafer, unlike with an n-type wafer, and the THz emission intensity is qualitatively proportional to the product of local electron mobility and diffusion potential, and is inversely proportional to penetration depth, all of which have a strong correlation with the quality of the materials and defects/impurities in them.

show abstract

“…Since these typically have wavelengths in the NIR, they can be focused to a diffraction-limited spot much smaller than THz frequency pulses, giving an improved imaging resolution by more than two orders of magnitude [145]. For example, integrated circuits have been imaged with a spatial resolution down to 1 µm [146], but the method has also been used to study physical processes in THz radiating materials [147][148][149][150][151][152] or processes on the surface of the radiating semiconductor [153][154][155]. Recently, the spatial resolution of LTEM was improved even further by implementing it in an s-SNOM microscope where a gold nanorod was imaged on a THz radiating InAs substrate (Figure 11) [156].…”

Section: Variations Of S-snom Configuration For Thz Imagingmentioning

confidence: 99%

Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Keiser

Klarskov

2019

Photonics

View full text Add to dashboard Cite

This article reviews recent advances in terahertz science and technology that rely on confining the energy of incident terahertz radiation to small, very sub-wavelength sized regions. We focus on two broad areas of application for such field confinement: metamaterial-based nonlinear terahertz devices and terahertz near-field microscopy and spectroscopy techniques. In particular, we focus on field confinement in: terahertz nonlinear absorbers, metamaterial enhanced nonlinear terahertz spectroscopy, and in sub-wavelength terahertz imaging systems.

show abstract

Probing the surface potential of oxidized silicon by assessing terahertz emission

Cited by 32 publications

References 20 publications

Simplified formulas for the generation of terahertz waves from semiconductor surfaces excited with a femtosecond laser

Simplified formulas for the generation of terahertz waves from semiconductor surfaces excited with a femtosecond laser

Terahertz Emission Spectroscopy and Microscopy on Ultrawide Bandgap Semiconductor β-Ga2O3

Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Contact Info

Product

Resources

About