Free-Carrier Infrared Absorption in III-V Semiconductors III. GaAs, InP, GaP and GaSb

Haga, Eijirô; Kimura, Hiroyuki

doi:10.1143/jpsj.19.658

Cited by 100 publications

(14 citation statements)

References 14 publications

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“…The significant deviation of r from the value 2 predicted by the Drude formula indicates that the Drude model cannot be applied to estimate the carrier density and wave number dependence of the FCA in n-type GaAs, because the energy dependence of the free-carrier scattering processes has been neglected. shows the measured values (dots) of ␣ FC ͑͒ versus n for bulk, n-type GaAs samples obtained at 300 K. Our measured values are in good agreement with published data [6][7][8] indicated by the open squares in Fig. 2.…”

Section: ͑1͒supporting

confidence: 89%

“…From the measured values of the constant C, we have determined ␣ WG ͑ 0 ͒ using Eqs. (6) and 7by assuming a wave-numberindependent gain coefficient g a = 7.2 cm kA −1 and ⌫ = 0.31 as discussed in the preceding section. The obtained values for ␣ WG ͑ 0 ͒, which are listed in Table I, are clearly smaller than the calculated data taking into account FCA in the WGs and in the four doped layers of each period of the cascade structure (Sec.…”

Section: Experimental Determination Of the Waveguide Losses In Twmentioning

confidence: 99%

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Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Giehler

Kostial

Hey

et al. 2004

Journal of Applied Physics

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GaAs/ Al 0.33 Ga 0.67 As quantum-cascade lasers with plasmon-assisted waveguides exhibit a decreasing threshold current density j th with increasing wave number 0 of the laser line, which changes as a function of the injector doping density. We have developed an analytical approach based on the effective dielectric tensor component for the p-polarized light emitted from a quantum-cascade laser, which explains the observed dependence of j th ͑ 0 ͒ in terms of losses due to free-carrier absorption predominantly in the doped waveguides ␣ WG ͑ 0 ͒. A contribution to the losses by free-carrier absorption in the quantum-cascade structure itself and subsequently to j th can be neglected except for very high injector doping densities. The calculated values for ␣ WG ͑ 0 ͒ are in good agreement with the experimental data. Our approach quantitatively predicts the observed decrease of j th from 17 to 7 kA cm −2 with increasing 0 between 900 and 1100 cm −1. In addition to achieving a direct physical insight into the influence of free-carrier absorption on the laser performance, the proposed analytical approach provides a simple tool for the determination of the waveguide losses for any quantum-cascade laser without adopting a numerical solver.

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Section: ͑1͒supporting

confidence: 89%

Section: Experimental Determination Of the Waveguide Losses In Twmentioning

confidence: 99%

Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Giehler

Kostial

Hey

et al. 2004

Journal of Applied Physics

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“…Free carrier absorption is stronger in S2 due to higher doping. Such wavelength dependence α ∝ λ 2.3 is typical for complex absorption by acoustic, optical phonons and impurities 29 . Second, dashed lines indicate defect photoionization spectra fits (several defects per sample).…”

Section: Resultsmentioning

confidence: 92%

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Ščajev

Mekys

Subačius

et al. 2022

Sci Rep

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Cadmium telluride (CdTe) semiconductors are used in thin-film photovoltaics, detectors, and other optoelectronic applications. For all technologies, higher efficiency and sensitivity are achieved with reduced charge carrier recombination. In this study, we use state-of-the-art CdTe single crystals and electro-optical measurements to develop a detailed understanding of recombination rate dependence on excitation and temperature in CdTe. We study recombination and carrier dynamics in high-resistivity (undoped) and arsenic (As)-doped CdTe by employing absorption, the Hall effect, time-resolved photoluminescence, and pump-probe in the 80–600 K temperature range. We report extraordinarily long lifetimes (30 µs) at low temperatures in bulk undoped CdTe. Temperature dependencies of carrier density and mobility reveal ionization of the main acceptors and donors as well as dominant scattering by ionized impurities. We also distinguish different recombination defects. In particular, shallow AsTe and deep VCd−AsCd acceptors were responsible for p-type conductivity. AX donors were responsible for electron capture, while nonradiative recombination centers (VCd−AsTe, As2 precipitates), and native defects (VCd−TeCd) were found to be dominant in p-type and n-type CdTe, respectively. Bimolecular and surface recombination rate temperature dependencies were also revealed, with bimolecular coefficient T−3/2 temperature dependence and 170 meV effective surface barrier, leading to an increase in surface recombination velocity at high temperatures and excitations. The results of this study allowed us to conclude that enhanced crucible rotation growth of As-doped CdTe is advantageous to As activation, leading to longer lifetimes and larger mobilities and open-circuit voltages due to lower absorption and trapping.

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“…We have previously shown that (GaN) 1– x (ZnO) x powder samples exhibit a broad absorption feature well below their direct optical gap (2.5–3.4 eV, depending on x ) in which the absorption rapidly increases with decreasing photon energy . This absorption feature is ascribed to the interaction of light with free carriers based on its functional form (continually increases with decreasing energy, as is observed in other semiconductor systems − ), and can be quantitatively fit to scaling relationships initially determined for single crystal samples of ZnO . In the present work, optical spectroscopy is used to investigate the influence of annealing (GaN) 1– x (ZnO) x samples on their free carrier concentration.…”

Section: Introductionmentioning

confidence: 99%

Influence of Thermal Annealing on Free Carrier Concentration in (GaN)_1–x(ZnO)_x Semiconductors

et al. 2017

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It was previously demonstrated that the efficiency of (GaN)1–x (ZnO) x semiconductors for solar water splitting can be improved by thermal annealing, though the origin of this improvement was not resolved. In the present work, it is shown that annealing reduces the free carrier (electron) concentration of (GaN)1–x (ZnO) x . The time-, temperature-, and atmosphere-dependent changes were followed through two simple techniques: indirect diffuse reflectance measurements from 0.5 to 3.0 eV which show very high sensitivity to the free carrier response at the lowest energies and EPR measurements which directly probe the number of unpaired electrons. For the thermal annealing of investigated compositions, it is found that temperatures of 250 °C and below do not measurably change the free carrier concentration, a gradual reduction of the free carrier concentration occurs over a time period of many hours at 350 °C, and the complete elimination of free carriers happens within an hour at 550 °C. These changes are driven by an oxidative process which is effectively suppressed under actively reducing atmospheres (H2, NH3) but which can still occur under nominally inert gases (N2, Ar). Surprisingly, it is found that the N2 gas released during thermal oxidation of (GaN)1–x (ZnO) x samples remains trapped within the solid matrix and is not expelled until temperatures of about 900 °C, a result directly confirmed through neutron pair-distribution fuction (PDF) measurements which show a new peak at the 1.1 Å bond length of molecular nitrogen after annealing. Preliminary comparative photoelectrochemical (PEC) measurements of the influence of free carrier concentration on photoactivity for water oxidation were carried out for a sample with x = 0.64. Samples annealed to eliminate free carriers exhibited no photoactivity for water oxidation, while a complex dependence on carrier concentration was observed for samples with intermediate free carrier concentrations. The methods demonstrated here provide an important approach for quantifying (and controlling) the carrier concentrations of semiconductors which are only available in the form of loose powders, as is commonly the case for oxynitride compounds.

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Free-Carrier Infrared Absorption in III-V Semiconductors III. GaAs, InP, GaP and GaSb

Cited by 100 publications

References 14 publications

Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Influence of Thermal Annealing on Free Carrier Concentration in (GaN)_1–x(ZnO)_x Semiconductors

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Free-Carrier Infrared Absorption in III-V Semiconductors III. GaAs, InP, GaP and GaSb

Cited by 100 publications

References 14 publications

Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Effect of free-carrier absorption on the threshold current density of GaAs∕(Al,Ga)As quantum-cascade lasers

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Influence of Thermal Annealing on Free Carrier Concentration in (GaN)1–x(ZnO)x Semiconductors

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Influence of Thermal Annealing on Free Carrier Concentration in (GaN)_1–x(ZnO)_x Semiconductors