Effects of neutron and electron irradiation on the absorption edge of GaAs

1991 ◽  
Vol 69 (3-4) ◽  
pp. 324-328 ◽  
Author(s):  
M. Parenteau ◽  
C. Carlone ◽  
M. Aubin ◽  
S. M. Khanna ◽  
W. T. Anderson ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Absorption Edge ◽  
Thermal Neutrons ◽  
Direct Absorption ◽  
Direct Edge ◽  
Transmission Measurements ◽  
Means Of Transmission ◽  
Insulating Liquid ◽  
Absorption Tail

Semi-insulating liquid encapsulated Czochralski GaAs wafers were submitted to irradiation with 1 MeV neutrons, thermal neutrons, 7 MeV electrons, and white electrons (up to 7 MeV). The direct absorption edge was then studied by means of transmission (T = 15 K) and thermoreflectance (T = 35 and 51 K) measurements. Thermoreflectance spectra showed that the position of the exciton does not shift after irradiation with 1 MeV neutrons, but that its broadening parameter Γ increases as the fluence increases. Transmission measurements have revealed the presence of two acceptor levels (C and Zn) in the unirradiated samples. The absorption associated with these impurities increased by a factor of 10 after irradiation with 1 MeV neutrons. This effect was not produced by the three other types of radiation. However, an absorption tail extending well below the direct edge is seen after irradiation with all four types of particles. A model proposed by Toyozawa fits this continuum quite well, suggesting that irradiation causes amorphization of the crystal. The rate of introduction of defects and its dependence on irradiation fluence is different for each type of radiation.

Intrinsic Optical Absorption in Germanium

1964 ◽  
Vol 19 (5) ◽  
pp. 548-552
Author(s):  
Günther Harbeke
Keyword(s):  
Optical Absorption ◽  
Low Temperatures ◽  
Energy Difference ◽  
Direct Absorption ◽  
Band Structure Calculations ◽  
Bulk Single Crystals ◽  
Transmission Measurements ◽  
Absorption Constant ◽  
Valence Bands ◽  
Structure Calculations

The absorption constant of germanium beyond the first direct absorption edge has been determined up to energies of 2.5 eV by transmission measurements on very thin samples prepared from bulk single crystals. The results are discussed in terms of recent band structure calculations and previous reflection measurements. At low temperatures the observed structure gives evidence for exciton formation connected with direct transitions at a saddle point in the energy difference between conduction and valence bands.

Structural Properties of Amorphous Silicon Produced by Electron Irradiation

1999 ◽  
Vol 557 ◽  
Author(s):  
J. Yamasaki ◽  
S. Takeda
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Distribution Function ◽  
Structural Properties ◽  
Electron Irradiation ◽  
Low Temperatures ◽  
Crystalline Silicon ◽  
Transmission Electron ◽  
Amorphous Si ◽  
Means Of Transmission

AbstractThe structural properties of the amorphous Si (a-Si), which was created from crystalline silicon by 2 MeV electron irradiation at low temperatures about 25 K, are examined in detail by means of transmission electron microscopy and transmission electron diffraction. The peak positions in the radial distribution function (RDF) of the a-Si correspond well to those of a-Si fabricated by other techniques. The electron-irradiation-induced a-Si returns to crystalline Si after annealing at 550°C.

Pressure dependence of the lowest direct absorption edge of ZnTe

1987 ◽  
Vol 61 (5) ◽  
pp. 275-278 ◽  
Author(s):  
K. Strössner ◽  
S. Ves ◽  
Chul Koo Kim ◽  
M. Cardona
Keyword(s):  
Absorption Edge ◽  
Pressure Dependence ◽  
Direct Absorption

No-Phonon and Phonon-Assisted Indirect Transitions in Si1−xGex Single Crystals

1996 ◽  
Vol 450 ◽  
Author(s):  
A. Gerhardt
Keyword(s):  
Single Crystals ◽  
Absorption Edge ◽  
Energy Gap ◽  
Differential Method ◽  
Composition Analysis ◽  
Calibration Function ◽  
Absorption Properties ◽  
Transmission Measurements ◽  
Threshold Energies ◽  
Phonon Transition

ABSTRACTThe absorption properties of high quality bulk Si1−xGex single crystals (0 ≤ × ≤ 0.16) are studied. Transmission measurements were performed at the indirect absorption edge. The shape of the absorption edge is characterized by structures attributed to the onset of no-phonon and phonon-assisted indirect optical transitions. Threshold energies have been determined using a differential method. A corrected calibration function for the dependence of the excitonic energy gap on composition is presented for the compositions, where x ranges from 0 to 0.16. The presented calibration function can be used for the composition analysis by an optical method. The analysis is independent of absolute transmission values.A simulation of the absorption spectra by calculations based on second order perturbation theory was used to fit the experimental data This procedure allows to estimate the oscillator strength of the no-phonon transition in dependence on x.

THE DIRECT ABSORPTION EDGE IN COVALENT SOLIDS

1967 ◽  
Vol 11 (4) ◽  
pp. 138-140 ◽  
Author(s):  
David Redfield ◽  
Martin A. Afromowitz
Keyword(s):  
Absorption Edge ◽  
Direct Absorption

Effect of hydrostatic pressure on the direct absorption edge of germanium

1977 ◽  
Vol 15 (2) ◽  
pp. 875-879 ◽  
Author(s):  
Benjamin Welber ◽  
Manuel Cardona ◽  
Yet-Ful Tsay ◽  
Bernard Bendow
Keyword(s):  
Hydrostatic Pressure ◽  
Absorption Edge ◽  
Direct Absorption ◽  
Effect Of Hydrostatic Pressure

Tunable Second-Harmonic Studies of Gan Films Near the Fundamental Bandedge

1994 ◽  
Vol 339 ◽  
Author(s):  
Joseph Miragliotta ◽  
Wayne A. Bryden ◽  
Thomas J. Kistenmacher ◽  
Dennis K. Wickenden
Keyword(s):  
Photon Energy ◽  
Absorption Edge ◽  
Nonlinear Response ◽  
Second Harmonic ◽  
Wide Bandgap ◽  
Second Order ◽  
Nonlinear Susceptibility ◽  
Transmission Measurements

ABSTRACTTunable second-harmonic (SH) transmission measurements were performed on a series of GaN films epitaxially deposited onto (OOOl)-oriented sapphire. Analysis of the nonlinear response showed an increase in the second-order nonlinear susceptibility (χ(2)ijk) when the photon energy of the SH field was tuned above the absorption edge in each respective film. Specifically, the magnitude of the χ(2)zxx element in χ(2)ijk reached a maximum of 0.5 × 10-7 e.s.u. just above the the fundamental bandgap with a dispersion similar to the predicted nonlinear response in wide-bandgap cubic zincblende II-VI semiconductors such as ZnSe.

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