THz-excitation spectroscopy technique for band-offset determination

Karpus, V.; Norkus, Ričardas; Butkutė, Renata; Stanionytė, Sandra; Čechavičius, Bronislovas; Krotkus, A.

doi:10.1364/oe.26.033807

Cited by 16 publications

(13 citation statements)

References 21 publications

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“…The strains and epitaxial splitting Δe in the bismide layers can be easily calculated for given values of elastic constants C12/C11 = 0.46 and the deformation potential b = −2 eV, which for dilute GaAsBi can be taken to be equal to those of GaAs. 31,32 The calculated epitaxial splitting is about Δe ~ 45 meV at the Bi concentration x = 0.05. Therefore, the ordering-induced splitting in the investigated dilute bismide samples should be of the order Δc ~ 40 meV or more.…”

Section: B Polarized Photoluminescencementioning

confidence: 95%

Polarization dependent photoluminescence and optical anisotropy in CuPtB-ordered dilute GaAs1–xBix alloys

Paulauskas

Čechavičius

Karpus

et al. 2020

Journal of Applied Physics

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The GaAs1-xBix semiconductor alloy allows to achieve large bandgap reduction and enhanced spin-orbit splitting energy at dilute Bi quantities. The bismide is currently being developed for near-to midinfrared lasers, multi-junction solar cells, and photodetectors. In this structure-property relationship study of GaAsBi alloys, we report polarization dependent photoluminescence that reaches ratio up to 2.4 at room temperature. Polarization dependence is also presented using transmittance spectra, and also birefringence and linear dichroism. The optical anisotropy observations agree with predictions of point symmetry reduction in the CuPtB-type ordered GaAsBi phase. The structural ordering is investigated experimentally from the atomic-scale in molecular-beam epitaxy (MBE) grown samples on exact and miscut (001) GaAs substrates, as well as a sample composed of anti-phase domains in which the ordering axes are rotated by right angles. Since the conditions stabilizing the CuPtB ordered phase fall within the typical MBE growth regime of dilute bismides, the optical anisotropy in GaAsBi alloys is expected to be ubiquitous. These findings are important for the future development of GaAsBibased optoelectronics and also provide new means to analyze structurally complex bismide alloys.

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Section: B Polarized Photoluminescencementioning

confidence: 95%

Polarization dependent photoluminescence and optical anisotropy in CuPtB-ordered dilute GaAs1–xBix alloys

Paulauskas

Čechavičius

Karpus

et al. 2020

Journal of Applied Physics

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“…A number of theoretical and experimental works have been devoted to the determination of these important parameters; those works are summarized in a review [ 78 ]. The terahertz excitation spectroscopy as a new way of estimating the energy band offsets is proposed in the paper [ 9 ]. If the layer with a narrower energy band gap is thin enough and on top of the sample, after illuminating it with femtosecond optical pulses, stronger THz emission would start only when the excess energy of excited electrons exceeded the energy offset in the conduction band ( Figure 21 ).…”

Section: Heterostructure Band Offsetsmentioning

confidence: 99%

“…They made it possible to obtain femtosecond optical pulses with wavelengths covering a wide spectral range and, therefore, study the dynamics of electrons excited at various initial energies within materials. Among the results obtained using femtosecond OPA pulses, one can distinguish the energy determination of additional conduction band valleys in semiconductors [ 8 ] and the line-up of energy bands in semiconductor heterojunctions [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Semiconductor Characterization by Terahertz Excitation Spectroscopy

2023

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Surfaces of semiconducting materials excited by femtosecond laser pulses emit electromagnetic waves in the terahertz (THz) frequency range, which by definition is the 0.1–10 THz region. The nature of terahertz radiation pulses is, in the majority of cases, explained by the appearance of ultrafast photocurrents. THz pulse duration is comparable with the photocarrier momentum relaxation time, thus such hot-carrier effects as the velocity overshoot, ballistic carrier motion, and optical carrier alignment must be taken into consideration when explaining experimental observations of terahertz emission. Novel commercially available tools such as optical parametric amplifiers that are capable of generating femtosecond optical pulses within a wide spectral range allow performing new unique experiments. By exciting semiconductor surfaces with various photon energies, it is possible to look into the ultrafast processes taking place at different electron energy levels of the investigated materials. The experimental technique known as the THz excitation spectroscopy (TES) can be used as a contactless method to study the band structure and investigate the ultrafast processes of various technologically important materials. A recent decade of investigations with the THz excitation spectroscopy method is reviewed in this article. TES experiments performed on the common bulk A3B5 compounds such as the wide-gap GaAs, and narrow-gap InAs and InSb, as well as Ge, Te, GaSe and other bulk semiconductors are reviewed. Finally, the results obtained by this non-contact technique on low-dimensional materials such as ultrathin mono-elemental Bi films, InAs, InGaAs, and GaAs nanowires are also presented.

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“…THz emission due to ballistic photoexcited electron propagation has been exploited for the measurements of conduction band offsets in GaAsBi/GaAs [14] and GaInAsBi/InP [15] heterojunctions. Femtosecond optical pulses with a tunable central wavelength were illuminating the interface between the air and the narrower bandgap material layer.…”

Section: Introductionmentioning

confidence: 99%

Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents

Malevich

Ziaziulia

Norkus

et al. 2021

Sensors

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Terahertz radiation pulses emitted after exciting semiconductor heterostructures by femtosecond optical pulses were used to determine the electron energy band offsets between different constituent materials. It has been shown that when the photon energy is sufficient enough to excite electrons in the narrower bandgap layer with an energy greater than the conduction band offset, the terahertz pulse changes its polarity. Theoretical analysis performed both analytically and by numerical Monte Carlo simulation has shown that the polarity inversion is caused by the electrons that are excited in the narrow bandgap layer with energies sufficient to surmount the band offset with the wide bandgap substrate. This effect is used to evaluate the energy band offsets in GaInAs/InP and GaInAsBi/InP heterostructures.

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THz-excitation spectroscopy technique for band-offset determination

Cited by 16 publications

References 21 publications

Polarization dependent photoluminescence and optical anisotropy in CuPtB-ordered dilute GaAs1–xBix alloys

Polarization dependent photoluminescence and optical anisotropy in CuPtB-ordered dilute GaAs1–xBix alloys

Semiconductor Characterization by Terahertz Excitation Spectroscopy

Terahertz Pulse Emission from Semiconductor Heterostructures Caused by Ballistic Photocurrents

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