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Izadifard, Morteza
Publications (10 of 31) Show all publications
Buyanova, I., Chen, W., Izadifard, M., Pearton, S., Bihler, C., Brandt, M., . . . Tu, C. (2007). Hydrogen passivation of nitrogen in GaNAs and GaNP alloys: How many H atoms are required for each N atom?. Applied Physics Letters, 90(2), 021920
Open this publication in new window or tab >>Hydrogen passivation of nitrogen in GaNAs and GaNP alloys: How many H atoms are required for each N atom?
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2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 2, p. 021920-Article in journal (Refereed) Published
Abstract [en]

Secondary ion mass spectrometry and photoluminescence are employed to evaluate the origin and efficiency of hydrogen passivation of nitrogen in GaNAs and GaNP. The hydrogen profiles are found to closely follow the N distributions, providing unambiguous evidence for their preferential binding as the dominant mechanism for neutralization of N-induced modifications in the electronic structure of the materials. Though the exact number of H atoms involved in passivation may depend on the conditions of the H treatment and the host matrixes, it is generally found that more than three H atoms are required to bind to a N atom to achieve full passivation for both alloys. © 2007 American Institute of Physics.

National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-38832 (URN)10.1063/1.2425006 (DOI)45825 (Local ID)45825 (Archive number)45825 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Buyanova, I., Bergman, P., Chen, W., Izadifard, M., Hong, Y. & Tu, C. (2007). Role of nitrogen in photoluminescence up-conversion in GaInNP/GaAs heterostructures. In: Wolfgang Jantsch, Friedrich Schaffler (Ed.), AIP Conference Proceedings / Volume 893. Paper presented at PHYSICS OF SEMICONDUCTORS: 28th International Conference on the Physics of Semiconductors - ICPS 2006, Vienna, Austria, 24-28 July 2006 (pp. 381-382). American Institute of Physics (AIP)
Open this publication in new window or tab >>Role of nitrogen in photoluminescence up-conversion in GaInNP/GaAs heterostructures
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2007 (English)In: AIP Conference Proceedings / Volume 893 / [ed] Wolfgang Jantsch, Friedrich Schaffler, American Institute of Physics (AIP), 2007, p. 381-382Conference paper, Published paper (Other academic)
Abstract [en]

Alloying of disordered GaInP with nitrogen is shown to lead to very efficient PLU in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy (GS‐MBE). This is attributed to the N‐induced changes in the band alignment at the GaInNP/GaAs heterointerface from the type I for the N‐free structure to the type II in the samples with N compositions exceeding 0.5%. Based on the performed excitation power dependent measurements, a possible mechanism for the energy upconversion is suggested as being due to the two‐step two‐photon absorption. The photon recycling effect is shown to be important for the structures with N=1%, from time‐resolved PL measurements. © 2007 American Institute of Physics

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2007
Series
AIP Conference Proceedings, ISSN 0094-243X ; 893
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-39124 (URN)10.1063/1.2729925 (DOI)46765 (Local ID)46765 (Archive number)46765 (OAI)
Conference
PHYSICS OF SEMICONDUCTORS: 28th International Conference on the Physics of Semiconductors - ICPS 2006, Vienna, Austria, 24-28 July 2006
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27
Izadifard, M. (2006). Optical characterization of dilute nitride semiconductors and related quantum structures. (Doctoral dissertation). Institutionen för fysik, kemi och biologi
Open this publication in new window or tab >>Optical characterization of dilute nitride semiconductors and related quantum structures
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dilute nitrides (i.e. nitrogen-containing, anion-mixed III-V ternary and quaternary alloys) have recently attracted much attention due to their unusual fundamental properties promising for device applications in optoelectronics and photonics, such as highly efficient and low cost near infrared lasers, efficient visible light emitting diodes (LEDs), multi-junction solar cells, as well as heterojunction bipolar transistors (HBTs). In order to fully explore the potential of these new materials, detailed knowledge on their fundamental and material-related properties is required.

The work presented in this thesis focuses on optical studies of the electronic structure, radiative recombination processes and also characterization of material properties of several dilute nitrides systems that are relevant to device applications, such as GaNP/GaP, GaNP/Si, GaNAs/GaAs and GaInNP/GaAs. The thesis is divided into two parts. The first part includes five chapters that give a general introduction to the research field and also describes experimental methods utilized in the research work. The second part contains seven original scientific papers.

Papers I and II report detailed studies of effects of post-growth hydrogen incorporation on the electronic structure of GaNAs and GaNP alloys by using photoluminescence (PL), PL excitation (PLE), and Raman spectroscopies, as well as high resolution X-ray diffraction (HRXRD) measurements. Introduction of hydrogen in the alloys was found to cause passivation of N-related localized states. Additionally, profound and rather astonishing changes in the band structure upon H incorporation were observed, such as a recovery of the bandgap energies of the parental GaAs and GaP, i.e. deactivation of the N-induced bandgap bowing. In GaNP, this was accompanied by a reduction in the N-induced coupling between the conduction band states. Raman spectroscopy has showed that these effects are related to hydrogeninduced breaking of the Ga-N bond. Raman and HRXRD measurements have also shown that the hydrogenation caused a strong expansion of the GaNP lattice, which changes the sign of strain from tensile strain in the as-grown GaNP epilayers to compressive strain after hydrogenation, due to formation of complexes between N and H.

Paper III-IV discuss optical quality and defect properties of GaNP/Si and GaNP /GaP alloys, as well as effects of rapid thermal annealing (RTA). By employing a variety of optical characterization techniques including cathodoluminescence (CL), cw- and time-resolved PL, PLE, and optically detected magnetic resonance (ODMR), high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates was demonstrated and was shown to be comparable to that of the “state-of-the-art" GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitials (Gai). A reduction and removal of competing non-radiative point defects by RTA has been concluded to be responsible for a substantial increase in radiative efficiency of the GaNP epilayers subjected to the post-growth annealing, evident from reduced thermal quenching of the PL intensity as well as from a substantial increase in carrier lifetime at room temperature.

Papers V-VII are devoted to detailed studies of Ga0.46In0.54NxP1-x alloys lattice matched to GaAs, by using cw- and time-resolved PL, PLE, and optically detected cyclotron resonance (ODCR) measurements. The type-II band alignment at the Ga0.46In0.54NxP1-x/GaAs interface was concluded with x ≥ 0.5% based on (i) highly efficient photoluminescence upconversion (PLU) observed in the N containing alloys and (ii) appearance of a near-infrared PL emission attributed to the spatially indirect type-II transitions. Compositional dependence of the conduction band offset at the GayIn1-yNxP1-x/GaAs interface was also estimated. Origin of the PLU process was determined as being due to two-step two-photon absorption (TS-TPA). Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to largely arise from radiative transitions involving spatially separated localized electronhole pairs. The observed charge separation was tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006. p. 53
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 995
Keywords
Dilute nitrides, optoelectronics, photonics
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-7290 (URN)91-85457-97-3 (ISBN)
Public defence
2006-02-10, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Available from: 2006-09-07 Created: 2006-09-07 Last updated: 2012-11-14
Izadifard, M., Bergman, P., Chen, W., Buyanova, I. A., Hong, Y. & Tu, C. (2006). Photoluminescence upconversion in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy. Journal of Applied Physics, 99(7), 073515
Open this publication in new window or tab >>Photoluminescence upconversion in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy
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2006 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 7, p. 073515-Article in journal (Refereed) Published
Abstract [en]

Properties of photoluminescence (PL) upconversion (PLU) in GaInNP/GaAs heterostructures are studied in detail by employing a number of optical spectroscopies. Based on excitation power dependent and temperature dependent PL measurements, the upconverted PL from GaInNP under optical excitation below its band gap is attributed to radiative transitions involving spatially separated localized electron-hole pairs, which is of a similar origin as the near-band-gap emission detected under optical excitation above the GaInNP band gap. The PLU process is shown to be largely promoted by increasing N content in the GaInNP alloys, due to a N-induced change in the band alignment at the GaInNP/GaAs heterointerface from the type I in the N-free structure to the type II in the samples with N compositions exceeding 0.5%. A possible mechanism for the energy upconversion is discussed in terms of two-step two-photon absorption. The photon recycling effect is shown to be important for the structures with N = 1%.

National Category
Engineering and Technology Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-50252 (URN)10.1063/1.2188087 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Izadifard, M., Bergman, P., Chen, W., Buyanova, I., Hong, Y. & Tu, C. (2006). Radiative recombination of GaInNP alloys lattice matched to GaAs. Applied Physics Letters, 88(1), 011919
Open this publication in new window or tab >>Radiative recombination of GaInNP alloys lattice matched to GaAs
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2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 1, p. 011919-Article in journal (Refereed) Published
Abstract [en]

Cw- and time-resolved photoluminescence (PL) spectroscopy is employed to evaluate dominant mechanisms for light emission in GayIn1−yNxP1−x alloys grown by gas source molecular-beam epitaxy on GaAs substrates. Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to be largely attributed to radiative transitions involving spatially separated localized electron-hole pairs. The observed charge separation is tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.

National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-36494 (URN)10.1063/1.2161118 (DOI)31451 (Local ID)31451 (Archive number)31451 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Vorona, I., Mchedlidze, T., Izadifard, M., Buyanova, I. A., Chen, W., Hong, Y. & Tu, C. (2006). Signatures of grown-in defects in GaInNP alloys grown on a GaAs substrate from magnetic resonance studies. Physica. B, Condensed matter, 376, 571-574
Open this publication in new window or tab >>Signatures of grown-in defects in GaInNP alloys grown on a GaAs substrate from magnetic resonance studies
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2006 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, p. 571-574Article in journal (Refereed) Published
Abstract [en]

Three grown-in defects acting as centers of non-radiative recombination (NR) were detected in GaInNP alloys grown on a GaAs substrate using the optically detected magnetic resonance (ODMR) technique. Among them, one was proposed to be either a Ga-i-related defect or an AS(Ga)-related defect, from the resolved four-line hyperfine structure. The former model was concluded to be more favorable by weighing physical properties of the two defects, e.g. the likelihood for their presence in the studied structures, their spatial location, g-value and effect of rapid thermal annealing (RTA). RTA at 700 degrees C was shown to reduce concentrations of the studied defects but it introduced a new defect that likely directly participates in the monitored radiative recombination process in the RTA-treated samples. (c) 2005 Elsevier B.V. All rights reserved.

Keywords
dilute nitrides, GaInNP, defect, magnetic resonance
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46031 (URN)10.1016/j.physb.2005.12.144 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Buyanova, I. A., Izadifard, M., Seppänen, T., Birch, J., Chen, W., Pearton, S., . . . Tu, C. (2006). Unusual effects of hydrogen on electronic and lattice properties of GaNP alloys. Physica. B, Condensed matter, 376, 568-570
Open this publication in new window or tab >>Unusual effects of hydrogen on electronic and lattice properties of GaNP alloys
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2006 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, p. 568-570Article in journal (Refereed) Published
Abstract [en]

Hydrogen incorporation is shown to cause passivation of various N-related localized states and partial neutralization of N-induced changes in the electronic structure of the GaNxP1-x alloys with x < 0.008. According to the performed X-ray diffraction measurements, the hydrogenation is also found to cause strong expansion of the GaNP lattice which even changes from a tensile strain in the as-grown GaNP epilayers to a compressive strain in the post-hydrogenated structures with the highest H concentration. By comparing results obtained using two types of hydrogen treatments, i.e. by implantation from a Kaufman source and by using a remote dc H plasma, the observed changes are shown to be inherent to H due to its efficient complexing with N atoms, whereas possible effects of implantation damage are only marginal. (c) 2005 Elsevier B.V. All rights reserved.

Keywords
hydrogen, passivation, GaNP, electronic structure
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46030 (URN)10.1016/j.physb.2005.12.143 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Izadifard, M., Mtchedlidze, T., Vorona, I., Chen, W., Buyanova, I. A., Hong, Y. & Tu, C. (2005). Band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy. Applied Physics Letters, 86(26), 261904
Open this publication in new window or tab >>Band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy
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2005 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 26, p. 261904-Article in journal (Refereed) Published
Abstract [en]

Low-temperature photoluminescence (PL), PL excitation, and optically detected cyclotron resonance measurements are employed to determine band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy. The type II band alignment at the Ga0.46In0.54NxP1−x/GaAs interface is concluded for the alloys with x ≥ 0.5% based on (i) highly efficient PL upconversion observed in the N containing samples and (ii) appearance of a near-infrared PL emission attributed to the spatially indirect type II transitions. Compositional dependence of the conduction band offset at the Ga1−yInyNxP1−x/GaAs interface is also estimated.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-50479 (URN)10.1063/1.1952586 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Buyanova, I., Izadifard, M., Chen, W., Xin, H., Tu, C. & Pearton, S. (2005). Effects of N incorporation on the electronic structure of GaNP: Origin of the 2.87 eV optical transition. Paper presented at 2005 APS March Meeting. Bulletin of the American Physical Society, vol. 50, 50
Open this publication in new window or tab >>Effects of N incorporation on the electronic structure of GaNP: Origin of the 2.87 eV optical transition
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2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Temperature dependent photoluminescence excitation (PLE) spectroscopy is employed to evaluate basic physical properties of the 2.87 eV absorption peak, recently discovered (I. A. Buyanova et al, PRB 69, 201303 (2004)) in the GaNxP1-x alloys. Whereas appearance of this transition is found to be facilitated by incorporation of N and also H atoms, its intensity does not scale with N content. This questions a possible association of this feature with a N-related localized state. Based on the results of temperature dependent measurements, the involved state is concluded to have a non-$\Gamma $ character. Excitation of the known N-related localized states via this state is found to be non-selective, opposed to that between the N-related centers. The observed properties are shown to be hardly consistent with those predicted for the higher lying localized state of the isolated N atom derived from the Γ conduction band minimum (CBM). Alternative explanations for the ``2.87 eV'' state as being due to either a t2 component of the X3c (or L1c CBM or a level arising from a complex of N and H (in some form) are also discussed.

Place, publisher, year, edition, pages
Bulletin of the American Physical Society, vol. 50: , 2005
National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-30794 (URN)16421 (Local ID)16421 (Archive number)16421 (OAI)
Conference
2005 APS March Meeting
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-03-27
Izadifard, M., Buyanova, I., Bergman, P., Chen, W., Utsumi, A., Furukawa, Y., . . . Yonezu, H. (2005). Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy. Semiconductor Science and Technology, 20(5), 353-356
Open this publication in new window or tab >>Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy
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2005 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 5, p. 353-356Article in journal (Refereed) Published
Abstract [en]

Temperature-dependent photoluminescence (PL), PL excitation and time-resolved PL measurements were employed to study the effects of rapid thermal annealing (RTA) on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy. A substantial increase in radiative efficiency of GaNP epilayers, which is especially pronounced for the high-energy PL component, was achieved after RTA and is attributed to annealing out of competing non-radiative centres. The latter is evident from reduced quenching of the PL intensity with increasing measurement temperature, which results in a strong increase (up to 18 times) in the PL intensity at room temperature (RT), as well as from a substantial increase in carrier lifetime at RT deduced from time-resolved PL measurements.

National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-30725 (URN)10.1088/0268-1242/20/5/005 (DOI)16338 (Local ID)16338 (Archive number)16338 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
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