| 1. |
- Buyanova, Irina, 1960-, et al.
(author)
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Effect of electron irradiation on optical properties of gallium nitride
- 1999
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In: Physica Scripta. - 0031-8949 .- 1402-4896. ; T79, s. 72-75
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Journal article (peer-reviewed)abstract
- The effect of electron irradiation on the optical properties of GaN epilayers is studied in detail by photoluminescence (PL) spectroscopy. The most common types of GaN material are used, i.e. strained heteroepitaxial layers grown on 6H SiC or Al2O3 substrates, and thick bulk-like layers with the conductivity varying from n-type to semi-insulating and p-type. The main effects of electron irradiation on all investigated samples are found to be as follows: (i) a radiation-induced quenching of excitonic emissions in the near band gap region; (ii) an appearance of broad overlapping PL emissions within the spectral range 0.7-1.1 eV and (iii) the appearance of a PL band with a sharp no-phonon (NP) line at around 0.88 eV followed by a rich phonon assisted sideband. The 0.88 eV band is shown to originate from an internal transition of a deep defect. With increasing temperature a hot PL line can be observed at about 2-4 meV above the NP line, originating from higher lying excited states of the defect. The electronic structure of the 0.88 eV defect is shown to be very sensitive to the internal strain field in the GaN epilayers.
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| 2. |
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| 3. |
- Buyanova, Irina, 1960-, et al.
(author)
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Effect of growth temperature on photoluminescence of GaNAs/GaAs quantum well structures
- 1999
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 75:24, s. 3781-
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Journal article (peer-reviewed)abstract
- The effect of growth temperature on the optical properties of GaAs/GaNxAs1-x quantum wells is studied in detail using photoluminescence (PL) spectroscopies. An increase in growth temperature up to 580 °C is shown to improve the optical quality of the structures, while still allowing one to achieve high (>3%) N incorporation. This conclusion is based on: (i) an observed increase in intensity of the GaNAs-related near-band-edge emission; (ii) a reduction in band-edge potential fluctuations, deduced from the analysis of the PL line shape; and (iii) a decrease in concentration of some extended defects detected under resonant excitation of the GaNAs. The thermal quenching of the GaNAs-related PL emission, however, is almost independent of the growth temperature and is attributed to a thermal activation of an efficient nonradiative recombination channel located in the GaNAs layers.
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| 4. |
- Buyanova, Irina, 1960-, et al.
(author)
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Electronic structure of the 0.88-eV luminescence center in electron-irradiated gallium nitride
- 1999
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In: Physical review. B, Condensed matter and materials physics. ; 60:3, s. 1746-1751
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Journal article (peer-reviewed)abstract
- Photoluminescence (PL) spectroscopy is employed to determine the nature of a near-infrared PL emission with a no-phonon line at ∼0.88 eV, commonly present in electron-irradiated GaN. This PL emission is suggested to originate from an internal transition between a moderately shallow excited state (with an ionization energy ∼21 meV) and the deep ground state (with an ionization energy ∼900 meV) of a deep defect. The existence of a higher-lying second excited state related to the 0.88-eV PL center is also shown from temperature-dependent studies. A different electronic character of the wave functions related to the first and second excited states has been revealed by PL polarization measurements. Since the PL emission has been observed with comparable intensity in all electron-irradiated GaN samples independent of doping on the starting material, it is proposed that either native defects, or common residual contaminants or their complexes are involved. The substitutional ON donor (or related complex) is considered as the most probable candidate, based on the observed striking similarity in the local vibrational properties between the 0.88-eV PL centers and the substitutional OP donor in GaP.
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| 5. |
- Buyanova, Irina, 1960-, et al.
(author)
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Intrinsic modulation doping in InP-based structures : properties relevant to device applications
- 1999
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In: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 201-202, s. 786-789
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Journal article (peer-reviewed)abstract
- In this work we study device-relevant issues, such as doping efficiency and thermal stability, of recently proposed intrinsic modulation doping approach where intrinsic defects (PIn antisites) are used as a carrier source instead of impurity dopants. The InP/InGaAs heterostructure designed to resemble high electron mobility transistor (HEMT) structures, where all the layers were grown at a normal growth temperature 480°C except for the top InP layer which was grown at 265°C, was used as a prototype device. A comparison between the intrinsically doped structure with extrinsically doped HEMTs, which have an identical design except that the top InP layer was instead Si-doped and was grown at 480°C, reveals a high efficiency of the intrinsic doping. The thermal stability of the intrinsically doped HEMT is examined by annealing at temperatures 400-500°C relevant to possible processing steps needed in device fabrication. The observed severe reduction of the carrier concentration after annealing performed without phosphorous gas protection is attributed to the known instability of an InP surface at T>400°C. Thermal stability of the intrinsically doped HEMT is shown to be improved by using an InP cap layer grown at 480°C.
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| 6. |
- Buyanova, Irina, 1960-, et al.
(author)
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Mechanism for Light Emission in GaNAs/GaAs Structures Grown by Molecular Beam Epitaxy
- 1999
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In: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 216:1, s. 125-129
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Journal article (peer-reviewed)abstract
- A detailed photoluminescence (PL) study reveals that the low-temperature PL emission in GaNAs epilayers and GaAs/GaNxAs1 - x quantum well structures grown by molecular beam epitaxy is governed by recombination of localized excitons. This conclusion is based on the analysis of the PL lineshape, its dependence on the excitation power and measurement temperature, as well as PL transient data. The depth of the localization potential is estimated as about 60 meV, varying slightly among the different structures.
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| 7. |
- Buyanova, Irina, 1960-, et al.
(author)
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Mechanism for low-temperature photoluminescence in GaNAs/GaAs structures grown by molecular-beam epitaxy
- 1999
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 75:4, s. 501-
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Journal article (peer-reviewed)abstract
- The mechanism for low-temperature photoluminescence (PL) emissions in GaNAs epilayers and GaAs/GaNxAs1 - x quantum well (QW) structures grown by molecular-beam epitaxy is studied in detail, employing PL, PL excitation, and time-resolved PL spectroscopies. It is shown that even though quantum confinement causes a strong blueshift of the GaNAs PL emission, its major characteristic properties are identical in both QW structures and epilayers. Based on the analysis of the PL line shape, its dependence on the excitation power and measurement temperature, as well as transient data, the PL emission is concluded to be caused by a recombination of excitons trapped by potential fluctuations in GaNAs.
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| 8. |
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| 9. |
- Buyanova, Irina, 1960-, et al.
(author)
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Thermal stability and doping efficiency of intrinsic modulation doping in InP-based structures
- 1999
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 75:12, s. 1733-
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Journal article (peer-reviewed)abstract
- Doping efficiency and thermal stability of intrinsic modulation doping in InP/InGaAs heterostructures, where intrinsic defects (PInantisites) are used as an electron source, are investigated. A high efficiency of the intrinsic doping is demonstrated from a comparison between the intrinsically doped and conventional extrinsically doped structures. The thermal stability of the intrinsically doped heterostructures is shown to be largely affected by the thermal stability of the InP surface.
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| 10. |
- Chen, Weimin, 1959-, et al.
(author)
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Optical and Microwave Double Resonance of III-nitrides
- 1999
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In: Joint International Meeting the 196th Meeting of The Electrochemical Society ECS and the 1999 Fall Meeting of The Electrochemical Society of Japan ECSJ,1999. ; , s. 764-
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Conference paper (other academic/artistic)abstract
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