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

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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
Electrical behavior of 4H-SiC metal-oxide-semiconductor structures with Al2O3 as gate dielectric
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
Show others and affiliations
2005 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, no 12, 124507- p.Article in journal (Refereed) Published
Abstract [en]

The electrical properties of Al2O3 as a gate dielectric in metal-oxide-semiconductorstructures based on n- and p-type 4H-SiC grown by sublimation method have been investigated and compared to the properties of similar structures utilizing SiO2. The electrically active defects in the structures are studied by capacitance–voltage (C–V) and current–voltage (I–V) methods. The results show that the type as well as spatial and energy distributions of defects in Al2O3/SiC and SiO2/SiC samples are different. The structures with Al2O3 on p-type 4H-SiC demonstrate much better electrical characteristics than the p-type 4H-SiC/SiO2 structures. It is demonstrated that the conduction process in the former is governed by Fowler–Nordheim electron tunneling from the Al gate whereas in the latter the hole tunneling from SiC is the more probable process. This difference combined with the higher defect density in p-type SiC/SiO2 structures defines the higher leakage currents compared to the structures utilizing Al2O3.

Place, publisher, year, edition, pages
2005. Vol. 97, no 12, 124507- p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-30684DOI: 10.1063/1.1938267Local ID: 16289OAI: oai:DiVA.org:liu-30684DiVA: diva2:251507
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-07
In thesis
1. Device characteristics of sublimation grown 4H-SiC layers
Open this publication in new window or tab >>Device characteristics of sublimation grown 4H-SiC layers
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

At present, focus of the SiC crystal growth development is on improving the crystalline quality without polytype inclusions, micropipes and the occurrence of extended defects. The purity of the grown material, as well as intentional doping must be well controlled and the processes understood. High-quality substrates will significantly improve device performance and yield. One of the aims of the licentiate thesis is further understanding of polytype inclusion formation as well as impurity control in SiC bulk crystals grown using PVT method also termed seeded sublimation method. We have identified a carbonization of the source as a major reason behind the polytype inclusion occurrence during the growth. The aim of this work was further understanding of sublimation growth process of 4H-SiC bulk crystals in vacuum, in absence of an inert gas. For comparison growth in argon atmosphere (at 5 mbar) was performed. The effect of the ambient on the impurity incorporation was studied for different growth temperatures. For better control of the process in vacuum, tantalum as a carbon getter was utilized.

The major focus of the thesis was put on further understanding of the PVT epitaxy with an emphasis on the high growth rate and the purity of grown layers.

High resistivity 4H-SiC samples grown by sublimation with high growth rate were studied. The measurements show resistivity values up to high 104 Ωcm. By correlation between the growth conditions and SIMS results, we apply a model in which it is proposed that an isolated carbon vacancy donor-like level is a possible candidate responsible for compensation of the shallow acceptors in p-type 4H-SiC. A relation between cathodoluminescence (CL) and DL TS data is taken into account to support the model.

To meet the requirements for high voltage blocking devices such as high voltage Schottky diodes and MOSFETs, 4H-SiC epitaxial layers have to exhibit low doping concentration in order to block reverse voltages up to few keV and at the same time have a low on-state resistance (Ron). High Ron leads to enhanced power consumption in the operation mode of the devices. In growth of thick layers for high voltage blocking devices, the conditions to achieve good on-state characteristics become more challenging due to the low doping and pronounced thicknesses needed, preferably in short growth periods. In case of high-speed epitaxy such as the sublimation, the need to apply higher growth temperature to yield the high growth rate, results in an increased concentration of background impurities in the layers as well as an influence on the intrinsic defects.

On-state resistance Ron estimated from current density-voltage characteristics of Schottky diodes on thick sublimation layers exhibits variations from tens of mΩ.cm2 to tens of Ω.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with increasing temperature was observed and its dependencies of T-1.3 and T-2.0 for moderately doped and low doped samples, respectively, were estimated. From deep level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on the on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism.

Metal-Oxide-Semiconductor (MOS) capacitors were fabricated and characterized on 4H-SiC epilayers grown by PVT (sublimation) epitaxy and compared to the properties of similar structures on CVD grown layers. Detailed investigations of the PVT structures indicate a stable behaviour of the interface traps from roomtemperature up to 475 K. The amount of positive oxide charges Qo is 6.83x109 cm-2 at room temperature and decreases with temperature increase which suggests temperature stability of processed devices. The density of interface states Dit obtained by AC conductance method is lower in the case of PVT sample.

AI203 as an alternative gate dielectric was studied. The implementation of this high-k dielectric is required in the case of high electric fields at which the usage of SiO2 may result in the reliability problems. The electrical properties of AI2O3 as a gate dielectric in MOS structures based on n- and p-type 4H-SiC grown by sublimation method were investigated and compared to the properties of similar structures utilizing SiO2.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 50 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1150
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-31210 (URN)16958 (Local ID)91-85297-50-X (ISBN)16958 (Archive number)16958 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-07

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Ciechonski, RafalSyväjärvi, MikaelYakimova, Rositsa

Search in DiVA

By author/editor
Ciechonski, RafalSyväjärvi, MikaelYakimova, Rositsa
By organisation
Semiconductor MaterialsThe Institute of Technology
In the same journal
Journal of Applied Physics
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 206 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • 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