Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Intervalley energy of GaN conduction band measured by femtosecond pump-probe spectroscopy
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.ORCID iD: 0000-0002-4606-4865
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
Show others and affiliations
2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 94, no 23, article id 235205Article in journal (Refereed) Published
Abstract [en]

Time-resolved transmission and reflection measurements were performed for bulk GaN at room temperature to evaluate the energy of the first conduction band satellite valley. The measurements showed clear threshold-like spectra for transmission decay and reflection rise times. The thresholds were associated with the onset of the intervalley electron scattering. Transmission measurements with pump and probe pulses in the near infrared produced an intervalley energy of 0.97±0.02 eV. Ultraviolet pump and infrared probe reflection provided a similar value. Comparison of the threshold energies obtained in these experiments allowed estimating the hole effective mass in the upper valence band to be 1.4m0. Modeling of the reflection transients with rate equations has allowed estimating electron-LO (longitudinal optical) phonon scattering rates and the satellite valley effective mass.

Place, publisher, year, edition, pages
American Physical Society, 2016. Vol. 94, no 23, article id 235205
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-202864DOI: 10.1103/PhysRevB.94.235205ISI: 000400687800005Scopus ID: 2-s2.0-85007564015OAI: oai:DiVA.org:kth-202864DiVA, id: diva2:1082603
Note

QC 20170317

Available from: 2017-03-17 Created: 2017-03-17 Last updated: 2018-05-21Bibliographically approved
In thesis
1. Optical properties of GaN and InGaN studied by time- and spatially-resolved spectroscopy
Open this publication in new window or tab >>Optical properties of GaN and InGaN studied by time- and spatially-resolved spectroscopy
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The past decade has seen rapid expansion in the use of group III-nitride based devices. White InGaN LEDs are substituting incandescent light bulbs, space satellite industry adopting ion-radiation-resistant GaN transistors, and AlGaN deep UV LEDs are increasingly being used for water disinfection and air purification. Despite this success, performance and efficiency of many devices is still far from optimal with many fundamental material properties still disputed and technological issues not solved. For example, the energy difference between the lowest conduction band valleys in the case of GaN is still being debated, and an efficient white light source of monolithic three-color LED has still not been achieved, due to the poor quantum efficiency of green-emitting quantum wells.

In view of these material challenges, this thesis was dedicated to studies of GaN, InGaN and their quantum wells with the help of time- and spatially- resolved spectroscopy and numerical modeling. This work provides new insights on both the fundamental and the growth-induced properties. Specifically, the energy difference between the lowest conduction band valleys in GaN, a key parameter for electronic devices, has been experimentally evaluated. In addition, electron scattering rates and satellite valley’s effective mass have been estimated by modeling pump-probe transients with rate equations. A study on Fe doped GaN has revealed that, depending on the device operation rate, different Fe+3 states should be considered when modelling GaN:Fe-based optoelectronic devices. Moreover, electron and hole capture coefficients and their temperature dependence have been determined. It has also been demonstrated that the random alloy model could only be used to describe emission and absorption linewidths in the InGaN alloy for a very low-In-content samples. Indium incorporation into the alloy has been found to be affected by the geometry of monolayer step edges that are formed during growth. Time-resolved scanning near-field photoluminescence spectroscopy studies on non-polar and semi-polar InGaN/GaN quantum wells have demonstrated that the common assumption of a spatially uniform radiative recombination rate is not always correct. Finally, it has been found that for a moderate to high-In-content QW the photoluminescence linewidth is defined primarily by variations of alloy composition and not well width fluctuations.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. p. 101
Series
TRITA-SCI-FOU ; 2018:19
Keywords
Gallium nitride, InGaN, near-field microscopy, photoexcited carrier dynamics, intervalley energy, Fe centers, In incorporation
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-228230 (URN)978-91-7729-805-2 (ISBN)
Public defence
2018-06-13, Sal C Elctrum, Kistagången 16, Kista, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180521

Available from: 2018-05-21 Created: 2018-05-20 Last updated: 2018-05-21Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Marcinkevičius, SauliusUŽdavinys, Tomas Kristijonas

Search in DiVA

By author/editor
Marcinkevičius, SauliusUŽdavinys, Tomas Kristijonas
By organisation
Materials- and Nano Physics
In the same journal
Physical Review B. Condensed Matter and Materials Physics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 81 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf