Presentation is loading. Please wait.

Presentation is loading. Please wait.

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.

Similar presentations


Presentation on theme: "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."— Presentation transcript:

1 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 Departamento de Ciencias – Sección Física – Grupo Ciencias de los Materiales Pontificia Universidad Católica del Perú (PUCP) San Miguel, 14th of April 2011

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

4 Example: Silicon Carbide (c-SiC) Schottky diode with high breakdown voltage High power electronics: Reduction of space and costs in a power source unit of a PC Band gap Breakdown voltage SiC3.0 eV5 MVcm -1 Si1.1 eV0.3 MVcm -1 Other applications: optoelectronics High frequency electronics High temperature devices

5 Band-gap engineering Variation of the band-gap by changing the composition The band-gap has influence on: Emission wavelength of an optical device efficiency of the light emission energy level of the dopants etc. Choose an optimal composition for a specific application A x B 1-x

6 Small overview of semiconductors Wide band-gap

7 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

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

9 Excitation mechanism 1 and 2: excitation paths a and b: recombination paths RE 3+ Ion Cathodoluminescense of RE 3+ in a-AlN:RE Intrashell-transitions of f-shells

10 Temperature quenching of Er 3+ doped semiconductors From Favennec: Electronics Letters 25 (1989) 718 a)In 0,16 Ga 0,38 As 0,84 P 0,16 b)Si c)InP d)GaAs e)Al 0,17 Ga 0,83 As f)ZnTe g)CdS Increase of band-gap

11 Temperature quenching for Er 3+ emission From Zanatta: Appl. Phys. Lett. 82 1395 (2003)

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

13 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

14 a-(SiC) x (AlN) 1-x :RE Why a-(SiC) x (AlN) 1-x ? Rare earth doping: Well defined emission color Covering of the whole color range Wide bandgap semiconductors: Increase of rare earth emission Lower temperature quenching Transparent Semiconductor devices 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

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

16 Los principios de magnetrón-sputtering Aumento de densidad de los ionesMás rapidez del crecimiento

17 El magnetrón magnetrón armado blindajeportatarget N N N S S S Anillo de plasma target

18 Schematics of the sputtering system Turbo- molecular pump Mechanical pump Pressure sensor Mass spectrometer control Ar N2N2 Mass flow controler Control of mass spectrometer Rf- generator shutter H2OH2O substrate targets flexible magnetrons H2OH2O match PC control

19 The rf magnetron sputter system at the PUCP Vacuum system: residual gas analysis Gas processing: flow control of N 2, H 2 and 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 cm 2 variable target substrate distance water cooled substrate holder

20 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 a-SiC 3´

21 80403 80402 80401 80331 80327 Característica de emisión de un magnetrón I

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

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

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

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

26 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 Bowing parameters: b 2 =(1.98±0.94) eV, b auc =(1.96±0.48) eV Fitting to Vegard´s law:

27 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

28 Emission of rare earth ions in a/nc-AlN and a-SiC Cathodoluminescense of RE 3+ in a-AlN:RE Cathodoluminescense of RE 3+ in a-SiC:RE

29 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

30 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 Tb 3+ emission in a-SiC

31 Thermal activation of a-(SiC) x (AlN) 1-x

32 Thermal activation of a-(SiC) 0.83 (AlN) 0.17 :Tb 3+

33 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

34 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)

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


Download ppt "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."

Similar presentations


Ads by Google