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  • 1
    Electronic Resource
    Electronic Resource
    Electron-paramagnetic-resonance spectra in as-grown CdGeAs2 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 435-437 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron-paramagnetic-resonance (EPR) has been used to investigate point defects in a single crystal of as-grown CdGeAs2. Spectra taken at 17 K with the magnetic field parallel to the c axis show a broad signal (∼165 Gauss wide) centered on gc=2.018 and a sharper signal (∼56 G wide) centered on gc=2.015. Together, these signals represent an unpaired-spin concentration of approximately 5×1019 cm−3. A single broad signal (∼165 G wide) centered on ga=1.995 is observed at 17 K when the magnetic field is along the a axis. It is suggested that these dominant EPR-active defects in CdGeAs2 consist of either a cation vacancy or an antisite cation with the unpaired spin shared by the four neighboring As ions. Additional weak EPR lines appear when the temperature is increased (from 17 to 40 K) and the microwave power is decreased (from 7 to 2.3 mW). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359600
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  • 2
    Electronic Resource
    Electronic Resource
    Direct measurement of ZnGeP2 birefringence from 0.66 to 12.2 μm using polarized light interference (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5942-5945 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The birefringence (Δn) of ZnGeP2 has been measured directly from polarized light interference spectra obtained in transmittance over the 0.66–12 μm wavelength range from samples of six different thicknesses. The Δn values were determined from the positions of fringe maxima (Δn=kλ/t) and then compared to previously published data which were obtained by a different technique. It was found that the interference fringe method results in values of Δn accurate to ±0.00005. The data are shown to exhibit much less scatter as a function of wavelength than previous results and can lead to more accurate calculations of phase-matching angles for second-harmonic generation applications. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359175
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  • 3
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance of Ni+ impurities in AgGaSe2 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 556-558 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR) has been used to detect Ni+ impurities substituting for Ag+ ions in a single crystal of AgGaSe2. The observed EPR spectrum has axial symmetry about the c axis of the crystal and is described by g(parallel)=2.635 and g⊥=2.241. A partially resolved hyperfine pattern in the c-axis spectrum is consistent with equivalent interactions with four I=3/2 nuclei (e.g., 69,71Ga). The concentration of Ni+ ions in the undoped crystal was approximately 7×1017 cm−3. These substitutional Ni+ impurity ions are suggested to be responsible for the polarized 2.2 μm absorption band that is presently limiting the use of AgGaSe2 as a 2 μm pumped optical parametric oscillator with mid-infrared output. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360865
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of defect-related optical absorption in ZnGeP2 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6677-6681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A broad optical absorption band with a peak near 1 μm is present in most single crystals of ZnGeP2. These same crystals have an electron paramagnetic resonance (EPR) signal which has been assigned to singly ionized zinc vacancies. A direct correlation between the intensity of the optical absorption at 1 μm and the intensity of the EPR signal has been established using a set of ZnGeP2 crystals where this absorption varied widely. These results suggest that the singly ionized zinc vacancy acceptor plays a direct role in the electronic transition(s) responsible for the 1 μm optical absorption. In separate experiments, it was found that illuminating the ZnGeP2 crystals with a He–Ne laser (632.8 nm) while at temperatures near 25 K produces an increase in the absorption at 1 μm and an increase in the zinc vacancy EPR spectrum. These latter results provide further evidence that the absorption at 1 μm is associated with the singly ionized zinc vacancy acceptor. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371743
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  • 5
    Electronic Resource
    Electronic Resource
    Infrared properties of AgGaTe2, a nonlinear optical chalcopyrite semiconductor (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 94-99 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fundamental optical properties of AgGaTe2, a nonlinear optical semiconductor are reported. These properties include birefringence, indices of refraction, infrared transmission, and the temperature dependence of the band gap. The average index for wavelengths greater than several microns was found to be 3.0. The birefringence was found to be rather large and to range from a near band edge value of 0.038 at 1.3 μm to a value of 0.017 at 15 μm. Additionally, native defect related sub-bandgap absorption, photoluminescence, and electrical transport have been studied in these nominally undoped p-type crystals. An activation energy associated with these defects was determined to be 0.3 eV and the corresponding photoluminescence and absorption data showed, respectively, a broad asymmetric emission band centered at 0.8 eV and two bands at 0.95 and 1.01 eV, the absorption band at 0.95 eV being the most intense. The measured properties were utilized to assess the potential of AgGaTe2 for the wavelength conversion processes of second-harmonic generation and degenerate optical parametric oscillation. It was found that AgGaTe2 will not phase match at room temperature. However, it is estimated that mixed crystals of the form AgGa(Se(1−x))Tex)2 for a Te addition of 19% can exceed the conversion efficiency of AgGaSe2 by more than 100%. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370704
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  • 6
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance study of a native acceptor in as-grown ZnGeP2 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1615-1617 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR) has been used to investigate an acceptor in as-grown single crystals of ZnGeP2. The spectra are characterized by equally spaced triplets with 1:2:1 intensity ratios representing hyperfine interactions (varying from 35 to 55 G in magnitude) with two equivalent phosphorous nuclei. Their angular dependence shows that there are four crystallographically equivalent orientations of the defect. The principal values of the g matrix are 2.002, 2.021, and 2.074 and the corresponding principal axes, at one of the four sites, are the [011], [1¯00], and [01¯1] directions, respectively. Two possible models are suggested for this acceptor: Either a zinc vacancy (VZn) or a zinc ion on a germanium site (ZnGe). It also is suggested that the acceptor responsible for the EPR signal is the same acceptor, namely AL1, that gives rise to a dominant near-infrared absorption band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111855
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  • 7
    Electronic Resource
    Electronic Resource
    Photoinduced electron paramagnetic resonance of the phosphorus vacancy in ZnGeP2 (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1758-1760 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron paramagnetic resonance (EPR) spectrum of the neutral phosphorus vacancy has been observed in as-grown ZnGeP2 during illumination at liquid-helium temperatures. Without illumination, this donor is a nonparamagnetic singly ionized phosphorus vacancy (VP+ center). Either above-band-gap light (514.5 nm) or below-band-gap light (632.8 nm) can produce the paramagnetic neutral state (VP0 center) of the donor. Principal values of the g matrix for the neutral donor are 1.944, 2.046, and 2.223. The angular dependence of the EPR spectrum suggests that the unpaired spin is unequally shared by two of the zinc ions neighboring the phosphorus vacancy. These phosphorus vacancies are the dominant donor in this highly compensated material, while the previously reported zinc vacancies are the dominant acceptor. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113358
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  • 8
    Electronic Resource
    Electronic Resource
    Polarized luminescence study of ordered nonlinear optical material ZnGeP2 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3142-3144 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarized photoluminescence (PL) and cathodoluminescence studies have been made as a function of excitation laser wavelength or electron beam energy for the ordered nonlinear optical material ZnGeP2 grown by the Bridgman method. The luminescence signal is seen to be strongly polarized. Furthermore, several PL peaks appear on top of one large broad band, and the dominant peak shifts to a higher energy position as the excitation energy increases. This observation can be explained by the transitions from three conduction bands (Γ6, Γ7, Γ7) to acceptor level one triplet ground state levels which parody the top three valence subbands (Γ6, Γ7, Γ6). This explanation agrees well with the theoretical energy band diagram of this pseudodirect band-gap material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111345
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  • 9
    Electronic Resource
    Electronic Resource
    Electron-nuclear double resonance of the zinc vacancy in ZnGeP2 (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2670-2672 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron-nuclear double resonance (ENDOR) has been used to identify the singly ionized zinc vacancy (VZn− center) in ZnGeP2. This S=1/2; defect is the dominant paramagnetic acceptor in the material, and it is associated with the absorption from 0.7 to 2.5 μm that limits the use of ZnGeP2 in optical parametric oscillators. The unpaired spin of the VZn− center is shared nearly equally by two phosphorus nuclei adjacent to the vacancy with little overlap of the wave function onto the other two phosphorus neighbors. Angular dependence of the ENDOR spectrum shows that the two primary 31P nuclei have nearly axial hyperfine matrices with unique axes pointing approximately toward the center of the vacancy. The internuclear axis for these two phosphorus makes an angle of 37.8° with the basal plane. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113120
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  • 10
    Electronic Resource
    Electronic Resource
    Optoelectronic effects in p-CdGeAs2 single crystals and structures based on them (1998)
    Springer
    Physics of the solid state 40 (1998), S. 190-194 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectra of inelastic light scattering by optical phonons in p-CdGeAs2 single crystals were obtained for the first time. The observed clear polarization dependence and the absence of any appreciable dependence of the intensity and frequency of the observed lines when the sample is swept in ≈300 µm steps indicates these CdGeAs2 single crystals grown by directional crystallization from a near-stoichiometric flux, are of high quality and homogeneous. The type of symmetry of the observed phonon lines is interpreted and it is shown that the force constants in CdGeAs2 and CdSnP2 crystals differ slightly. Temperature dependences of the electrical conductivity and the Hall constant were studied in oriented homogeneous p-CdGeAs2 single crystals. It was established that the conductivity of these crystals is determined by the deep acceptor level E A=0.175 eV and has the degree of compensation 0.5–0.6. The temperature dependence of the Hall mobility reflects the competition between impurity and lattice mechanisms of hole scattering. The photosensitivity of In/CdGeAs2 surface barrier structures reaches 20 µA/W at T=300 K and remains at this level within the fundamental absorption of CdGeAs2. It is concluded that these structures may be used as wide-band photoconverters for natural light and as selective photoanalyzers for linearly polarized radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130269
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