Indirect Absorption edge of In<sub>1–x</sub>Ga<sub>x</sub>P Mixed Crystals Studied by Wavelength Modulation

Donecker, J.; Kluge, J.

doi:10.1002/pssb.2220710143

Cited by 9 publications

(13 citation statements)

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“…the E,, E, + A, energies were taken from the minima of the DR spectra; a more detailed analysis gave only a negligible correction to the energies determined in this way. The DA spectra were evaluated as described in [14], i.e. the threshold energies were taken directly from the da/dE curves at the 9/10 amplitude of the maximum signal on its low-energy wing.…”

Section: Analpis Of Spectramentioning

confidence: 99%

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Lange¹,

Donecker²,

Friedrich³

1976

Physica Status Solidi (b)

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The direct E,, E, + A , and indirect E r -x transition energies of Ini-,Ga,P crystals are studied by electromodulation and wavelength modulation methods a t 77 K and room temperature. TheE, energy at 77 K and room temperature obeys a parabolic relation as a function of composition x with a bowing parameter of b = 0.764 and 0.76 eV, respectively. The E r -x energy a t 77 K can be expressed by a linear x-dependence with slope 0.072 eV. The crossover point a t 77 K is determined as xc = 0.72 0.015; E , = (2.300 f 0.003) eV. The spin-orbit splitting A, shows an upward bowing with bowing parameter -0.060 eV.

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Section: Analpis Of Spectramentioning

confidence: 99%

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Lange¹,

Donecker²,

Friedrich³

1976

Physica Status Solidi (b)

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Section: Introductionmentioning

confidence: 99%

“…Despite the CBM being X-like at x = 0.80, the coupling with the Γ-like state does yield a finite Γ component ~ 0.5 %, which is sufficient to produce the zero-phonon absorption or emission at the X-like fundamental bandgap. [9,10] It is worth mentioning that because of the high degeneracy of the VB, it is found that at x = 0.50 the spin-orbit split off band has only ~ 45% of the Γ component, even though being merely ~ 100 meV below the VBM, which might be reflected in the weakness of the spin-orbit feature in absorption and modulation spectra for samples with x ~ 0.5. [21] Another important finding is that there is a strong inter-valley mixing among the degenerate critical points k 0 's in the VCA, even in the case they are the CBM and have a high overall purity.…”

Section: Introductionmentioning

confidence: 99%

“…This system has been shown to exhibit zero-phonon absorption and emission even in the indirect band-gap region with small amount of In (< 10%). [9,10] It is also well known to exhibit spontaneous ordering when grown by MOCVD.[11] Besides being widely used in HBT's for telecommunications, the alloy with x ~ 0.5 is a key component in a lattice-matched three-junction solar cell (with GaAs and Ge) that has yielded a record efficiency of 34.7%. [12] We have previously investigated the electronic structure near the fundamental bandgap for x ~ 0.5 as a function of order parameter, using an empirical pseudopotential method (EPM), and achieved remarkably excellent agreement between experiment and theory.…”

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Non-Bloch Nature of Alloy States in a Conventional Semiconductor Alloy:GaxIn1−xPas an Example

2008

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Contrary to the conventional wisdom, electronic states in a "well behaved" semiconductor alloy such as Ga x In 1-x P may drastically deviate from a Bloch state, which can be true even for band edge states if they are derived from degenerate critical points.For Ga x In 1-x P in the entire composition range, k-space spectral analyses are performed for the important critical points, revealing the significance of the (near) resonant inter-and intra-valley scatterings of the fluctuation potential in the alloy. The non-trivial impications of such scatterings on the transport and strain effect are discussed. * yong_zhang@nrel.gov 1 An electronic state in a conventional semiconductor alloy A x B 1-x is often described in the same way as in a pure semiconductor, i.e., using a well defined k vector in the reduced Brillouin zone (BZ) within the framework of the "virtual crystal approximation (VCA)". [1,2] The conventional wisdom seems to suggest that the effect of disorder can be viewed as an energy shift from the VCA value plus a spectral broadening (at least for states near the band edge). [3,4] Indeed, it has been verified theoretically that a fundamental band edge state (either the conduction band minimum, CBM, or valence band maximum, VBM) does contain more than 90% of one particular k component of the BZ. [5] Therefore, it appears reasonable to classify the alloy state according to the Bloch state symmetry ("majority representation"), [5] with the understanding that the deviation from the VCA does make an alloy somewhat different from a pure semiconductor in certain important aspects. Among them, are the zerophonon emission and absorption at an indirect band gap, [6], a reduction in carrier mobility, [7] and various statistical effects such as the linewidth broadening in an optical transition.[8] However, it is not clear to what extent quantitatively the VCA picture remains useful for the global electronic structure of an alloy, i.e., including electronic states beyond the band edge (e.g., high lying critical points), and it has not been realized that there are subtle but important effects for the degenerate band edge states although at the first glance they seem to obey the "majority representation". [5] We now find that in a conventional alloy a large number of alloy states are surprisingly "non-Bloch" or it is not always appropriate to associate an alloy state with a well defined k point, and there are strong inter-valley scatterings among the degenerate critical points of the VCA. These 2 findings should have significant impacts on the understanding of optical and transport properties of the alloy in general.We have choosen the alloy system Ga x In 1-x P for this study. This system has been shown to exhibit zero-phonon absorption and emission even in the indirect band-gap region with small amount of In (< 10%). [9,10] It is also well known to exhibit spontaneous ordering when grown by MOCVD.[11] Besides being widely used in HBT's for telecommunications, the alloy with x ~ 0.5 is a key component in a latti...

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Magnetic circular dichroism of indirect excitonic transitions in GaP and In₁‐_xGa_xP

Donecker¹,

Kluge²

1976

Physica Status Solidi (b)

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Measurements of the magnetic circular dichroism (MCD) of the indirect absorption edge of intrinsic GaP and Inl-,Ga,P (z 2 0.77) a t temperatures from 2.5 to 300 K and at magnetic fields up to 52 kOe are reported. The fine structure of the indirect absorption edge is well resolved. The MCD peaks corresponding to LA and TA assisted indirect transitions have the same shape as the corresponding peaks in the wavelength modulated spectra, b u t the latter have different signs. That means that the thresholds of the indirect absorption edge are rigidly shifted by the magnetic field and the direction of the shift is connected with the type of the phonons. Additionally a n MCD peak appears in mixed crystals which corresponds to the no-phonon transition. It has the same sign as the LA-MCD peak. An attempt is made to interprete the experimental results by group theory within an exciton model. Further theoretical effort is necessary for a satisfactory explanation.Es wird uber Messungen des magnetischen Zirkulardichroismus (MCD) a n der indirekten Absorptionskante von undotiertem GaP und In1 _,Ga,P (z 2 0,77) bei Temperatwen zwischen 2,5 und 300 K und bei Magnetfeldern bis zu 52 kOe berichtet. Die Feiiistruktur der indirekten Absorptionskante ist gut aufgelost. Die MCD-Peaks, die LA-bzw. TAassistierten indirekten fibergiingen zuzuordnen sind, stimmen in der Form gut mit denen der entsprechenden wellenliingenmodulierten Spektren iiberein, haben jedoch im Unt,erschied zu letzteren unterschiedliche Vorzeichen. Das bedeutet, daO die Stufen in der indirekten Absorptionskante durch das magnetische Feld starr verschoben werden, daO die Richtung der Verschiebung jedoch mit der Phononenart zusammenhangt. I n Mischkristallen tritt zusiitzlich ein MCD-Peak auf, der dem No-Phonon-Ubergang entspricht und das Vorzeichen des LA-MCD-Peaks hat. Es wird ein Versuch unternommen, die experimentellen Ergebnisse mit gruppentheoretischen Mitteln innerhalb eines Exzitonenmodells zu erkliiren. Weitere theoretische Untersuchungen sind fur eine befriedigende Erkliirung notwendig.

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Indirect Absorption edge of In_1–xGa_xP Mixed Crystals Studied by Wavelength Modulation

Abstract: The advantages of the wavelength-modulation technique (1) a r e used here to in-Ga P mixed crystals and vestigate the weak structures in the indirect edge of In to observe the direct-indirect transition directly ~ because the corresponding x-value

Cited by 9 publications

References 11 publications

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Non-Bloch Nature of Alloy States in a Conventional Semiconductor Alloy:GaxIn1−xPas an Example

Magnetic circular dichroism of indirect excitonic transitions in GaP and In₁‐_xGa_xP

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Indirect Absorption edge of In1–xGaxP Mixed Crystals Studied by Wavelength Modulation

Abstract: The advantages of the wavelength-modulation technique (1) a r e used here to in-Ga P mixed crystals and vestigate the weak structures in the indirect edge of In to observe the direct-indirect transition directly ~ because the corresponding x-value

Cited by 9 publications

References 11 publications

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In1−xGaxP

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In1−xGaxP

Non-Bloch Nature of Alloy States in a Conventional Semiconductor Alloy:GaxIn1−xPas an Example

Magnetic circular dichroism of indirect excitonic transitions in GaP and In1‐xGaxP

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Indirect Absorption edge of In_1–xGa_xP Mixed Crystals Studied by Wavelength Modulation

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Electroreflectance and Wavelength Modulation Study of the Direct and Indirect Fundamental Transition Region of In_1−xGa_xP

Magnetic circular dichroism of indirect excitonic transitions in GaP and In₁‐_xGa_xP