1 / 34

Roland Weingärtner

Bandgap Engineering of the Amorphous Wide Band-Gap Semiconductor (SiC) 1- x (AlN) x Doped with Rare Earths and its Optical Emission Properties. Roland Weingärtner . San Miguel, 14th of April 2011. Departamento de Ciencias – Sección Física – Grupo Ciencias de los Materiales.

kapono
Télécharger la présentation

Roland Weingärtner

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bandgap Engineering of the Amorphous Wide Band-GapSemiconductor (SiC)1-x(AlN)xDoped with Rare Earths and itsOptical Emission Properties Roland Weingärtner San Miguel, 14th of April 2011 Departamento de Ciencias – Sección Física – Grupo Ciencias de los Materiales Pontificia Universidad Católica del Perú (PUCP)

  2. Outline I Motivation and Introduction • Wide band-gap semiconductors • Band-gap engineering • Rare earth doping and optical emission II First Results of a-(SiC)x(AlN)1-x • Thin film growth method and structural characterisation • Band-gap engineering of a-(SiC)x(AlN)1-x III Cathodoluminescense measurements • Spectral emission of rare earth doped a-(SiC)x(AlN)1-x • Thermal activation of rare earth emission IV Summary and Acknowledgements

  3. Why wide band-gap semiconductors ? Principal idea: Combine the advantages of an insulator and a semiconductor Advantage of a semiconductor: Active electronic devices like diodes, transistors, etc Advantage of an insulator: Due to the wide band-gap the samples are transparent Historic development: GaN based LED

  4. Band-gap engineering • The band-gap has influence on: • Emission wavelength of an optical device • efficiency of the light emission • energy level of the dopants • etc. AxB1-x Variation of the band-gap by changing the composition Choose an optimal composition for a specific application

  5. Small overview of semiconductors Wide band-gap

  6. Why rare earth doping in semiconductors ? • Optical emission properties of rare earths: • emission wavelength does not depend on the host material • Color is typical for a specific rare earth ion • Intensity of rare earth emission depends on the material: • band-gap quenching • temperature quenching • concentration quenching

  7. Colors in rare earth doped GaN M. Garter et al. Appl. Phys. Lett. 74 (1999) p.182

  8. Excitation mechanism Cathodoluminescense of RE3+ in a-AlN:RE Intrashell-transitions of f-shells RE3+ Ion 1 and 2: excitation paths a and b: recombination paths

  9. Temperature quenching of Er3+ doped semiconductors • In0,16Ga0,38As0,84P0,16 • Si • InP • GaAs • Al0,17Ga0,83As • ZnTe • CdS Increase of band-gap From Favennec: Electronics Letters 25 (1989) 718

  10. Temperature quenching for Er3+ emission From Zanatta: Appl. Phys. Lett. 82 1395 (2003)

  11. Temperature quenching in AlN:RE Phenomenological description: From Lozykowski and Jadwisienczak: Phys. Stat. Sol. B 244 (2007) 2109

  12. Outline I Motivation and Introduction • Wide band-gap semiconductors • Band-gap engineering • Rare earth doping and optical emission II First Results of a-(SiC)x(AlN)1-x • Thin film growth method and structural characterisation • Band-gap engineering of a-(SiC)x(AlN)1-x III Cathodoluminescense measurements • Spectral emission of rare earth doped a-(SiC)x(AlN)1-x • Thermal activation of rare earth emission IV Summary and Acknowledgements

  13. Why a-(SiC)x(AlN)1-x? • Wide bandgap semiconductors: • Increase of rare earth emission • Lower temperature quenching • Transparent • Semiconductor devices • Rare earth doping: • Well defined emission color • Covering of the whole color range a-(SiC)x(AlN)1-x:RE • Amorphous films: • Inexpensive • Simple production • Higher incorporation of rare earths • Pseudobinary compound: • Band-gap engineering (3eV to 6eV) • one composition parameter • Sputtering from SiC and AlN target

  14. Los principios de dc-sputtering sustrato + + + + + + + + - target 10-2 mbar 1000 V ánodo + ion Ar Átomo Ar electrón Problemas: Plasma frío: • Inestabilidad del plasma • Sólo targets metálicos • Baja eficiencia

  15. Los principios de magnetrón-sputtering Aumento de densidad de los iones Más rapidez del crecimiento

  16. El magnetrón portatarget blindaje Anillo de plasma target magnetrón armado N S S S N N

  17. Schematics of the sputtering system Mass spectrometer Control of mass spectrometer H2O shutter Mass flow controler substrate targets Pressure sensor Rf- generator Rf-generator flexible magnetrons Turbo-molecular pump H2O match control Mechanicalpump N2 PC control Ar

  18. The rf magnetron sputter system at the PUCP • Vacuum system: • residual gas analysis • Gas processing: • flow control of N2, H2and Ar: 0…100 sccm, 5N...6N • working pressure: Sputter targets: • trial magnetron sputtering, 2´´ • 3 Rf generators, P<300W • felxible target geometry !! Substrates: • Substrate area up to 128 cm2 • variable target substrate distance • water cooled substrate holder

  19. A typical film of a-SiC on glas Target material: Silicon Carbide (SiC) Substrate material: fused glas Rf power: 100 W Process gas: Argon, 5N Gas flow: 80 sccm Argon pressure: 810-3 mbar 3´ a-SiC 3´

  20. Característica de emisión de un magnetrón I 80403 80402 80401 80331 80327

  21. Característica de emisión de un magnetrón II emisión en uu. aa. Contorno de emisión 1cm plasma target N S S S blindaje N N imanes

  22. A typical thin film of a-(SiC)x(AlN)1-x EDX results host substrate • highly pure films (i.e. Na content < 8 ppm wt.) • no signature of impurities in the film

  23. Structure of a/nc-AlN and a-SiC anealed at 900°C Transmission electron microscopy (TEM): diffraction a/nc-AlN a-SiC Substrate (Si) High resolution transmission electron microscopy (HRTEM): a/nc-AlN There are nanocrystals embedded in an amorphous matrix

  24. Optical absorption measurements Determination of the band-gap i.e. a-(SiC)0.25(AlN)0.75:

  25. Band-gap engineering of a-(SiC)x(AlN)1-x [1] Nurmagomedov et al.: Sov. Phys. Semicond. 23 100 (1989) [2] Gurumurugan et al.: Appl. Phys. Lett. 74 3008 (1999) [3] Zanatta et al.: J. Phys. D: Appl. Phys. 42 (2009) 025109 Fitting to Vegard´s law: Bowing parameters: ba2=(1.98±0.94) eV , bTauc=(1.96±0.48) eV

  26. Outline I Motivation and Introduction • Wide band-gap semiconductors • Band-gap engineering • Rare earth doping and optical emission II First Results of a-(SiC)x(AlN)1-x • Thin film growth method and structural characterisation • Band-gap engineering of a-(SiC)x(AlN)1-x III Cathodoluminescense measurements • Spectral emission of rare earth doped a-(SiC)x(AlN)1-x • Thermal activation of rare earth emission IV Summary and Acknoledgements

  27. Emission of rare earth ions in a/nc-AlN and a-SiC Cathodoluminescense of RE3+ in a-AlN:RE Cathodoluminescense of RE3+ in a-SiC:RE

  28. Thermal activation of a-/nc-AlN • exponential growth with the anealing temperature • there is a saturation of the RE emission at anealing tempertures of 900°C

  29. Thermal activation of a-SiC • exponential growth with anealing temperature • there is no saturation up to 1000°C • there is an optimal anealing temperature for the Tb3+ emission in a-SiC

  30. Thermal activation of a-(SiC)x(AlN)1-x

  31. Thermal activation of a-(SiC)0.83(AlN)0.17:Tb3+

  32. Summary Wide-bandgap semiconductors • Rare earth doping • bandgap engineering First results on a-(SiC)x(AlN)1-x thin films • HRTEM investigations • bandgap engineering of a-(SiC)x(AlN)1-x Cathodoluminescense • optical emission of a-(SiC)x(AlN)1-x • thermal activation of rare earth emission • Conferences/Publications: • IMRC 2009 in Cancun, Mexico (invited talk) • ICSCRM´2009 in Nuremberg, Germany • Five publications in International Journals

  33. Acknowledgements Materials Department, University of Erlangen, Germany • Prof. Dr. Winnacker • Prof. Dr. H. P. Strunk • Catholic University of Lima, Peru (PUCP) • Prof. F. De Zela • Andrés Guerra, Gonzalo Galvez, Oliver Erlenbach (PhD) • Liz Montañez, Katia Zegarra, (Licenciatura) • This research work is supported by the • Pontificia Universidad Católica del Peru (PUCP) • Deutsche Forschungsgemeinschaft (DFG) and the • German Service of Academic Interchange (DAAD)

  34. Wide bandgap semiconductors From Steckl MRS Bull. 24, p. 33 (1999)

More Related