liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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
N-polar AlN nucleation layers grown by hot-wall MOCVD on SiC: Effects of substrate orientation on the polarity, surface morphology and crystal quality
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. SweGaN AB, Tekn Ringen 8D, S-58330 Linkoping, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. SweGaN AB, Tekn Ringen 8D, S-58330 Linkoping, Sweden.
Show others and affiliations
2020 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 580, article id 411819Article in journal (Refereed) Published
Abstract [en]

Hot-wall metalorganic vapor phase epitaxy enables a superior quality of group-III nitride epitaxial layers and high electron mobility transistor structures, but has not yet been explored for N-polar growth. In this work, we aim at achieving N-polar AlN nucleation layers (NLs) with optimized properties for subsequent growth of GaN device heterostructures. The effects of substrate orientation on the polarity, surface morphology and crystalline quality of AlN NLs on on-axis C-face SiC (000 (1) over bar), C-face SiC (000 (1) over bar) off-cut towards the [11 (2) over bar0] by 4 degrees, and Si-face SiC (0001) are investigated. The results are discussed in view of growth mode evolution with growth temperature and substrate orientation. It is demonstrated that N-polar AlN NLs with step-flow growth mode and 0002 rocking curve widths below 20 arcsec can be achieved on off-axis C-face SiC substrates.

Place, publisher, year, edition, pages
ELSEVIER , 2020. Vol. 580, article id 411819
Keywords [en]
Hot-wall; AlN nucleation layer; Nitrogen-polar; Substrate orientation effect; MOCVD
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:liu:diva-163650DOI: 10.1016/j.physb.2019.411819ISI: 000510641000018OAI: oai:DiVA.org:liu-163650DiVA, id: diva2:1394213
Conference
8th South African Conference on Photonic Materials (SACPM)
Note

Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA) under the Competence Center Program [2016-05190]; Linkoping University; Chalmers University of Technology; ABB; Ericsson; Epiluvac; FMV; Gotmic; On Semiconductor; Saab; SweGaN; UMS; Swedish Research Council VRSwedish Research Council [2016-00889]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [FL12-0181, RIF14-055, EM16-0024]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University, Faculty Grant SFO Mat LiU [2009-00971]

Available from: 2020-02-18 Created: 2020-02-18 Last updated: 2023-12-28
In thesis
1. Hot-wall MOCVD of N-polar group-III nitride materials
Open this publication in new window or tab >>Hot-wall MOCVD of N-polar group-III nitride materials
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Group III-Nitride semiconductors: indium nitride (InN), gallium nitride (GaN), aluminum nitride (AlN) and their alloys continue to attract significant scientific interest due to their unique properties and diverse applications in photonic and electronic applications. Group-III nitrides have direct bandgaps which cover the entire spectral range from the infrared (InN) to the ultraviolet (GaN) and to the deep ultraviolet (AlN). This makes III-nitride materials suitable for high-efficient and energy-saving optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes (LDs). The Nobel Prize in Physics 2014 was awarded for the invention of efficient GaN blue LEDs, which further accelerated the research in the field of group III-nitride materials. GaN and related alloys are also suitable for high-temperature, high-power and high-frequency electronic devices with performance that cannot be delivered by other semiconductor technologies such as silicon (Si) and gallium arsenide (GaAs). For example, GaN-based high electron mobility transistors (HEMTs) have been widely adopted for radio frequency (RF) communication and power amplifiers, high-voltage power switches in radars, satellites, and wireless base stations for 5G. 

Recently, nitrogen (N)-polar group-III nitrides have drawn much attention due to their advantages over their metal-polar counterparts in e.g. HEMTs. These include feasibility to fabricate ohmic contacts with low resistance, an enhanced carrier confinement with a natural back barrier, and improved device scalability. Despite intensive research, the growth of micrometer-thick high-quality N-polar GaN based materials remains challenging. One of the major problems to develop device-quality N-polar nitrides is the high surface roughness, which results from the formation of hexagonal hillocks or step-bunching. Another significant hurdle is the unintentional polarity inversion, which reduces the crystalline quality and prohibits device fabrication. 

This licentiate thesis focuses on the development of N-polar AlN and GaN heterostructures on SiC substrates for HEMT RF applications. The overall aim is to exploit the advantages of the hot-wall MOCVD concept to grow high-quality N-polar HEMT structures for higher operational frequencies and improved device performance. In order to achieve this goal, special effort is dedicated to understanding the effects of growth conditions and substrate orientation on the structural properties and polarity of AlN, GaN and AlGaN grown by hot-wall MOCVD. N-polar AlN nucleation layers (NLs) with layer by layer growth mode and step-flow growth mode can be achieved on on-axis and 4_ offaxis SiC (000¯1), respectively, by carefully controlling V/III ratio and growth temperature. Utilizing scanning transmission electron microscopy (STEM) we have established a comprehensive picture of the atomic arrangements, local polarity and polarity evolution in AlN, GaN/AlN and AlGaN/GaN/AlN in the cases of low-temperature and high-temperature AlN NLs both for on-axis and off-axis substrates. We have shown that typically employed methods for polarity determination using potassium hydroxide wet etching could not provide conclusive results in the case of mixed-polar AlN as Al-polar domains may be easily over-etched and remain undetected. Atomic scale electron microscopy is therefore needed to accurately determine the polarity. We further have developed growth strategy and have optimized the epitaxial process for N-polar GaN, and have demonstrated high quality N-polar AlGaN/GaN/AlN heterostructures.  

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2021. p. 48
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1865
National Category
Natural Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-175502 (URN)10.3384/lic.diva-175502 (DOI)9789179299309 (ISBN)
Presentation
2021-06-18, Jordan-Fermi (J402), F-Building, Campus Valla, Linköping, 13:00 (English)
Opponent
Supervisors
Funder
Vinnova, 2016 - 05190Linköpings universitetSwedish Research Council, 2016 - 00889,
Note

Additional funding agencies: Chalmers University of technology; ABB; Ericsson; Epiluvac; FMV; Gotmic; Saab; SweGaN; UMS; Swedish Foundation for Strategic Research under Grants No. FL12-0181, No. RIF14-055, and No. EM16-0024; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University, Faculty Grant SFO Mat LiU No.2009- 00971.

Available from: 2021-05-20 Created: 2021-05-05 Last updated: 2023-12-28Bibliographically approved
2. Hot-wall MOCVD of N-polar group-III nitride materials and high electron mobility transistor structures
Open this publication in new window or tab >>Hot-wall MOCVD of N-polar group-III nitride materials and high electron mobility transistor structures
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Group III-Nitride semiconductors: indium nitride (InN), gallium nitride (GaN), aluminum nitride (AlN) and their alloys continue to attract significant scientific interest due to their unique properties and diverse applications in photonic and electronic applications. Group-III nitrides have direct bandgaps which cover the entire spectral range from the infrared (InN) to the ultraviolet (GaN) and to the deep ultraviolet (AlN). This makes III-nitride materials suitable for high-efficient and energy-saving optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes (LDs). The Nobel Prize in Physics 2014 was awarded for the invention of efficient GaN blue LEDs, which further accelerated the research in the field of group III-nitride materials. GaN and related alloys are also suitable for high-temperature, high-power and high-frequency electronic devices with performance that cannot be delivered by other semiconductor technologies such as silicon (Si) and gallium arsenide (GaAs). For example, GaN-based high electron mobility transistors (HEMTs) have been widely adopted for radio frequency (RF) communication and power amplifiers, high-voltage power switches in radars, satellites, and wireless base stations for 5G.

Recently, nitrogen (N)-polar group-III nitrides have drawn much attention due to their advantages over their metal-polar counterparts in e.g. HEMTs. These include feasibility to fabricate ohmic contacts with low resistance, an enhanced carrier confinement with a natural back barrier, and improved device scalability. Despite intensive research, the growth of micrometer-thick high-quality N-polar GaN based materials remains challenging. One of the major problems to develop device-quality N-polar nitrides is the high surface roughness, which results from the formation of hexagonal hillocks or step-bunching. Another significant hurdle is the unintentional polarity inversion, which reduces the crystalline quality and prohibits device fabrication. 

This thesis focuses on the development of N-polar AlN and GaN heterostructures on SiC substrates for HEMT RF applications. The overall aim is to exploit the advantages of the hot-wall MOCVD concept to grow high-quality N-polar HEMT structures for higher operational frequencies and improved device performance. In order to achieve this goal, special effort is dedicated to understanding the effects of growth conditions and substrate orientation on the structural properties and polarity of AlN, GaN and AlGaN grown by hot-wall MOCVD. N-polar AlN nucleation layers (NLs) with layer by layer growth mode and step-flow growth mode can be achieved on on-axis and 4­ off-axis SiC (000¯1), respectively, by carefully controlling V/III ratio and growth temperature. Utilizing scanning transmission electron microscopy (STEM) we have established a comprehensive picture of the atomic arrangements, local polarity and polarity evolution in AlN, GaN/AlN and AlGaN/GaN/AlN in the cases of low-temperature and high-temperature AlN NLs both for on-axis and off-axis substrates. We have shown that the typically employed methods for polarity determination using potassium hydroxide wet etching could not provide conclusive results in the case of mixed-polar AlN as Al-polar domains may be easily over-etched and remain undetected. Atomic scale electron microscopy is therefore needed to accurately determine the polarity. A polarity control strategy has been developed by variation of thermodynamic Al supersaturation and substrates offcut angles in order to achieve desired growth mode and polarity. We further have developed growth strategy and have optimized the epitaxial process for N-polar GaN by multiple-step temperature processes on three types of C-face SiC substrates with different offcut angles. A highquality N-polar AlGaN/GaN/AlN heterostructure has been demonstrated. A 2DEG carrier density up to 1013 cm−2 have been demonstrated for N-polar HEMT structure. 

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2022. p. 66
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2239
Keywords
Nitrogen-polar, MOCVD, III-nitride, GaN, AlN, C-face SiC, HEMTs
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-187141 (URN)10.3384/9789179293918 (DOI)978-91-7929-390-1 (ISBN)978-91-7929-391-8 (ISBN)
Public defence
2022-09-08, Nobel (BL32), B-huset, Campus Valla, Linköping, 13:30 (English)
Opponent
Supervisors
Funder
Vinnova, 2016 - 05190Linköpings universitetSwedish Research Council, 2016 - 00889Swedish Foundation for Strategic Research, FL12-0181; RIF14-055; EM16-0024
Note

Additional funding agencies:

Chalmers University of technology; ABB; Ericsson; Epiluvac; FMV; Gotmic; On Semiconductor; Saab; SweGaN; UMS; Volvo Cars; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University, Faculty Grant SFO Mat LiU No.2009- 00971.

Available from: 2022-08-05 Created: 2022-08-05 Last updated: 2023-12-28Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Search in DiVA

By author/editor
Zhang, HengfangPaskov, PlamenKordina, OlleChen, Jr-TaiDarakchieva, Vanya
By organisation
Semiconductor MaterialsFaculty of Science & Engineering
In the same journal
Physica. B, Condensed matter
Other Physics Topics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 292 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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