Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

Dankowski, S. U.; Streb, D.; Ruff, M.; Kiesel, P.; Kneissl, Michael; Knüpfer, B.; Döhler, G. H.; Keil, U. D.; So/renson, C. B.; Verma, Ashish

doi:10.1063/1.116748

Cited by 43 publications

(22 citation statements)

References 9 publications

(11 reference statements)

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“…One possible mechanism noted in the literature [10,6] is the thermal shift of the bandgap leading to a higher absorption coefficient at a given wavelength. Absorption data for LT-GaAs over a wide energy range were measured in [19]. From these data a value of 17000/cm for the absorption coefficient of annealed LT-GaAs at 780 nm is obtained and the the expected absorption is 57% in a nominally 0.5 µm thick layer.…”

Section: Discussionmentioning

confidence: 99%

“…From these data a value of 17000/cm for the absorption coefficient of annealed LT-GaAs at 780 nm is obtained and the the expected absorption is 57% in a nominally 0.5 µm thick layer. The change in absorption is about 70000/cm/eV (linear fit to the data in [19]). Taking a common red-shift of the bandgap of GaAs of 0.3 nm/K, an enhancement of absorption by 4.5% would be expected from this argument.…”

Section: Discussionmentioning

confidence: 99%

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On the thermal dependence of the generation of terahertz radiation by photomixing

Campbell

Ackemann

Fraser

et al. 2014

Semicond. Sci. Technol.

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Abstract. We study the temperature dependence of the generation of Terahertz (THz) waves by photomixing in GaAs based antennas, grown at low-temperatures. For excitation with 780 nm light, the generated photocurrent increases by 15%, if the temperature is increased from 18 • C to 60 • C, whereas the generated THz power increases by 28%. The results show that the operation of THz antennas is robust with respect to changes in the ambient temperature and thus support the possibility of robust, potentially mobile devices without the need for a careful temperature control of the antenna structure.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

On the thermal dependence of the generation of terahertz radiation by photomixing

Campbell

Ackemann

Fraser

et al. 2014

Semicond. Sci. Technol.

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“…4 These midgap states are referred to in other literatures as defect states, deep energy level (EL) defects, deep traps, deep defects, and midgap defects. 3,[5][6][7][8] Defects in GaAs grown by molecular beam epitaxy (MBE) occur as a result of low-temperature growth in a range from 180 • C to 300 • C. This is lower than the normal epitaxial growth temperatures at around 580 • C to 600 • C. 9 Particle-induced x-ray (PIXE) analysis revealed that LT-GaAs consists of 1-1.25 at % excess As 10 which has been suggested as the source of the deep EL2-like defect (0.68 eV-0.92 eV). 8,[11][12][13] Several other deep-level defects were noted in experimental studies using electron paramagnetic resonance (EPR), thermally stimulated currents (TSC) spectra, deep level transient spectroscopy (DLTS) characterization, and deep center photoluminescence-excitation (PLE) spectra.…”

Section: Introductionmentioning

confidence: 99%

“…7,[13][14][15][16] Theoretical studies on the presence of these point defects and their role in the creation of deep-level states have been conducted for the bulk and unreconstructed surface of GaAs. 5,6,8,[17][18][19][20][21][22] For example, Li et al considered the ternary complex defect (As Ga V As V Ga ) in bulk GaAs, 5 Esteves et al investigated the isolated As Ga using cluster model for bulk, 6 Schultz explored the deep gallium antisite in bulk, 18 and El-Mellouhi et al studied self-vacancies. 20 Moreover, defects in (001) and (110) facets of surface were studied by Ma et al 17 and Williams et al, 21 respectively.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - β2(2x4)

et al. 2018

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We performed first-principles calculations based on density functional theory (DFT) to investigate the role of point defects in the structural, electronic, and optical properties of the GaAs(001)- β2(2x4). In terms of structural properties, AsGa is the most stable defect structure, consistent with experiments. With respect to the electronic structure, band structures revealed the existence of sub-band and midgap states for all defects. The induced sub-bands and midgap states originated from the redistributions of charges towards these defects and neighboring atoms. The presence of these point defects introduced deep energy levels characteristic of EB3 (0.97 eV), EL4 (0.52 eV), and EL2 (0.82 eV) for AsGa, GaAs, GaV, respectively. The optical properties are found to be strongly related to these induced gap states. The calculated onset values in the absorption spectra, corresponding to the energy gaps, confirmed the absorption below the known bulk band gap of 1.43 eV. These support the possible two-step photoabsorption mediated by midgap states as observed in experiments.

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“…At low intensity continuous wave (CW) illumination, the absorption in post-growth annealed LT-GaAs is indeed very low, and no quantitative data are present in the literature. 16,17 Last years, we developed vertically integrated LT-GaAs photoconductors working at 800 nm, which take advantage of Fabry-Pérot (FP) resonances to exhibit a high dc responsivity 18 and record performances when used as CW THz emitter 19 or detector. 20 In this structure, a sub-micron-thick LT-GaAs layer is sandwiched between two gold layers which serve at the same time as bias electrodes and optical mirror (see Fig.…”

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confidence: 99%

Resonant cavities for efficient LT-GaAs photoconductors operating at λ = 1550 nm

et al. 2016

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We show that photoconductors based on low-temperature-grown GaAs (LT-GaAs) can be efficiently operated by 1.55 μm telecom wavelength by using metallic mirror based optical cavities. Two different semi-transparent front mirrors are compared: the first one is a thin gold layer, whereas the second one consists of a gold grating. Light absorption in grating mirror based optical cavities is numerically, analytically, and experimentally investigated allowing for an appropriate optical design. We show a 3 times improvement of the LT-GaAs photoconductor photoresponse by using, as front mirror, the gold grating once compared with the thin gold layer. It reaches around 0.5 mA/W under continuous wave, whereas a transient photoresistivity (Ron) as low as 5 Ω is deduced from dc photocurrents measured under femtosecond pulsed laser excitation. This work paves the way to efficient and reliable optoelectronics systems for GHz or THz waves sampling driven by 1.55 μm pulsed lasers widely available.

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Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

Cited by 43 publications

References 9 publications

On the thermal dependence of the generation of terahertz radiation by photomixing

On the thermal dependence of the generation of terahertz radiation by photomixing

First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - β2(2x4)

Resonant cavities for efficient LT-GaAs photoconductors operating at λ = 1550 nm

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