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Semiconductor Nanostructures ISemiconductor Nanostructures I
H. von KänelH. von KänelH. von KänelH. von KänelLaboratorium für FestkörperphysikLaboratorium für Festkörperphysik
ETHZETHZ
Moore‘s LawMoore‘s LawMoore s LawMoore s Law
Doubling of transistor density in less than every 2 yearsDoubling of transistor density in less than every 2 years
Semiconductor Nanostructures
International Roadmap for SemiconductorsInternational Roadmap for SemiconductorsInternational Roadmap for SemiconductorsInternational Roadmap for Semiconductors
Semiconductor Nanostructures
Evolution of LED performanceEvolution of LED performanceEvolution of LED performanceEvolution of LED performance
Haitz law for red and blue LEDsHaitz law for red and blue LEDs
Semiconductor Nanostructures
M.R. Krames et al., J. Display Technol. M.R. Krames et al., J. Display Technol. 33, 160 (2007), 160 (2007)
Quantum efficiencies of HBLEDsQuantum efficiencies of HBLEDsQuantum efficiencies of HBLEDsQuantum efficiencies of HBLEDs
J M Philli t l L & Ph t R i 1 N 4 2007J M Philli t l L & Ph t R i 1 N 4 2007
Semiconductor Nanostructures
J.M. Phillips et al. Laser & Photon Review 1, No. 4, 2007J.M. Phillips et al. Laser & Photon Review 1, No. 4, 2007
Periodic table of elementsPeriodic table of elementsPeriodic table of elementsPeriodic table of elements
Semiconductor Nanostructures
Di d t tDi d t tDiamond structureDiamond structure
Semiconductor Nanostructures
ZiZi bl d t tbl d t tZincZinc--blende structureblende structure
Semiconductor Nanostructures
Comparison of wurtzite and zincComparison of wurtzite and zinc--ppblende structuresblende structures
Semiconductor Nanostructures
Tetrahedrally bonded semiconductorsTetrahedrally bonded semiconductors(diamond, zinc blende)(diamond, zinc blende)
Semiconductor Nanostructures
Variation of bandgap with lattice Variation of bandgap with lattice parameterparameter
UVUV--green group III nitridesgreen group III nitridesYellowYellow--red zinc blende arsenides red zinc blende arsenides -- phosphidesphosphides
Semiconductor Nanostructures
M.R. Krames et al., J. Display Technol. M.R. Krames et al., J. Display Technol. 33, 160 (2007), 160 (2007)
Consequences of strainConsequences of strainConsequences of strainConsequences of strain
Strain affects electronic structure, optical and Strain affects electronic structure, optical and t t tit t titransport propertiestransport properties
Strain affects crystal quality through defect Strain affects crystal quality through defect y q y gy q y gformationformation
Strain affects growth modesStrain affects growth modesStrain affects growth modesStrain affects growth modes
Strain affects the stability of phasesStrain affects the stability of phases
Semiconductor Nanostructures
Epitaxial growth modesEpitaxial growth modesEpitaxial growth modesEpitaxial growth modes
FrankFrank--van van der Merweder Merwe
VolmerVolmer--WeberWeber StranskiStranski--KrastanowKrastanow
Semiconductor Nanostructures
Semiconductor Nanostructures
Semiconductor Nanostructures
Structural data of group III nitridesStructural data of group III nitridesStructural data of group III nitridesStructural data of group III nitrides
Room temperature data forRoom temperature data for–– Lattice parametersLattice parameters–– Thermal expansionThermal expansion
Semiconductor Nanostructures
Thermal expansionThermal expansion
AlAl22OO33(0001) substrates(0001) substratesAlAl22OO33(0001) substrates(0001) substrates
Notice rotation of overlayer by 30 degrees!Notice rotation of overlayer by 30 degrees!
Semiconductor Nanostructures
Notice rotation of overlayer by 30 degrees!Notice rotation of overlayer by 30 degrees!Misfit for GaN f = Misfit for GaN f = --16.1 %16.1 %
Si(111) substratesSi(111) substratesSi(111) substratesSi(111) substrates
Misfit for GaN f = 16.9 %Misfit for GaN f = 16.9 %
Semiconductor Nanostructures
Strain relieving mechanismsStrain relieving mechanismsStrain relieving mechanismsStrain relieving mechanisms
Plastic relaxation: Formation of misfit Plastic relaxation: Formation of misfit dislocationsdislocations
Elastic relaxation: Surface corrugation, island Elastic relaxation: Surface corrugation, island formationformationformationformation
Formation of epitaxially stabilized phasesFormation of epitaxially stabilized phases
Semiconductor Nanostructures
Strain relaxation by dislocationsStrain relaxation by dislocationsStrain relaxation by dislocationsStrain relaxation by dislocations
a)a) Coherent interface, Coherent interface, compressively strained filmcompressively strained film
b)b) Incoherent interface, relaxed filmIncoherent interface, relaxed film
Semiconductor Nanostructures
compressively strained filmcompressively strained film
Critical thickness for plastic relaxationCritical thickness for plastic relaxationCritical thickness for plastic relaxationCritical thickness for plastic relaxation
a)a) Pure edge dislocations with Burgers vector b = 2.2 ÅPure edge dislocations with Burgers vector b = 2.2 Å
6060°° di l ti ith b 3 8 Ådi l ti ith b 3 8 Å
Semiconductor Nanostructures
b)b) 6060°° dislocations with b = 3.8 Ådislocations with b = 3.8 Å
Geometry of 60Geometry of 60--degree dislocationsdegree dislocationsGeometry of 60Geometry of 60 degree dislocationsdegree dislocations
(111)(111)
-b=a/2[011]
n
[110]
TD
� �
b=a/2[011]
p
(001)
MD
�
�m
p
[110]-
(001)
[110]
A.E. Blakeslee, MRS Symp. Proc. A.E. Blakeslee, MRS Symp. Proc. 148148, 217 (1989), 217 (1989)
Semiconductor Nanostructures
Propagation of dislocation loops Propagation of dislocation loops p g pp g pin {111} planesin {111} planes
Semiconductor Nanostructures
Dislocation control by patterningDislocation control by patterning
P. P. ZaumseilZaumseil et al. et al. J. Appl. J. Appl. PhysPhys 109 023511109 023511Phys.Phys. 109, 023511 109, 023511 (2011)(2011)
6060--degree dislocationsdegree dislocations
A.E. Blakeslee, MRS Symp. Proc. A.E. Blakeslee, MRS Symp. Proc. 148148, 217 (1989), 217 (1989)
Semiconductor Nanostructures
Aspect ratio trapping (ART)Aspect ratio trapping (ART)Aspect ratio trapping (ART)Aspect ratio trapping (ART)
Semiconductor Nanostructures
Lateral epitaxial overgrowth (LEO)Lateral epitaxial overgrowth (LEO)Lateral epitaxial overgrowth (LEO)Lateral epitaxial overgrowth (LEO)
Marachand et alMarachand et alMarachand et al.Marachand et al.
Appl. Phys. Lett. Appl. Phys. Lett. 7373, 747 (1998), 747 (1998)
1.1. Nucleation in mask openingsNucleation in mask openings2.2. Lateral overgrowthLateral overgrowth33 CoalescenceCoalescence
Semiconductor Nanostructures
3.3. CoalescenceCoalescence
Elastic strain relaxation by island Elastic strain relaxation by island formationformation
Semiconductor Nanostructures
Normalized free energy for island Normalized free energy for island gygyformationformation
F/FF/F aVaV3/23/2 b Vb VF/FF/Fc c = aV= aV3/2 3/2 –– b Vb V
Semiconductor Nanostructures
STM monitoring of Ge island STM monitoring of Ge island ggformation on Si(001)formation on Si(001)
l t lli W tipolycrystalline W tip
Vbias
sample
piezotube
It
sample tube
feedback z
x,y drive
Semiconductor Nanostructures
Shape evolution sequenceShape evolution sequenceShape evolution sequenceShape evolution sequenceShape evolution sequenceShape evolution sequenceShape evolution sequenceShape evolution sequenceA. Rastelli et al., Phys. Rev. Lett. A. Rastelli et al., Phys. Rev. Lett. 8787, 256101 (2001), 256101 (2001)
Prepyramid T-Pyramid Pyramid
Super DomeT-Dome Dome
Super-Dome
Semiconductor Nanostructures
70×70×11 nm3
120×120×27 nm3
GaN quantum dots on AlNGaN quantum dots on AlNGaN quantum dots on AlNGaN quantum dots on AlNHRTEMHRTEM STEMSTEM
T. Xu et al., J. Appl. Phys. T. Xu et al., J. Appl. Phys. 102102, 073517 (2007), 073517 (2007)
K. Hoshino et al., phys. Stat. Sol. (b) K. Hoshino et al., phys. Stat. Sol. (b) 240240, 322 (2003), 322 (2003)
Compressive misfit Compressive misfit –– 2.5 %2.5 %Truncated pyramidal shapeTruncated pyramidal shapeW tti l i ibl i STEMW tti l i ibl i STEM
Semiconductor Nanostructures
Wetting layer visible in STEMWetting layer visible in STEM
PbSe quantum dots on PbTe(111)PbSe quantum dots on PbTe(111)PbSe quantum dots on PbTe(111)PbSe quantum dots on PbTe(111)
G Springholz et al ScienceG Springholz et al Science 282282 734 (1998)734 (1998)
Semiconductor Nanostructures
G. Springholz et al., Science G. Springholz et al., Science 282282, 734 (1998), 734 (1998)
fcc ordering of dot SLfcc ordering of dot SLgg
G. Springholz et al.G. Springholz et al.
Science Science 282282, 734 (1998), 734 (1998)
Semiconductor Nanostructures
GaN columns on AlN/Si(111)GaN columns on AlN/Si(111)GaN columns on AlN/Si(111)GaN columns on AlN/Si(111)
Potential for columnar LEDs with much higher Potential for columnar LEDs with much higher li ht t ti ffi ili ht t ti ffi ilight extraction efficiencylight extraction efficiency
Semiconductor Nanostructures
Epitaxial stabilization of phasesEpitaxial stabilization of phasesEpitaxial stabilization of phasesEpitaxial stabilization of phases
Semiconductor Nanostructures
Cubic GaN/GaAs(001)Cubic GaN/GaAs(001)Cubic GaN/GaAs(001)Cubic GaN/GaAs(001)
A. Trampert and K. Ploog, A. Trampert and K. Ploog, C st Res TechnolC st Res Technol 3535Cryst. Res. Technol. Cryst. Res. Technol. 3535, , 793 (2000)793 (2000)
Misfit 20%!Misfit 20%!C i id l i 5C i id l i 5 44
Semiconductor Nanostructures
Coincidence lattice 5 aCoincidence lattice 5 acc--GaN GaN = 4 a= 4 aGaAsGaAs
Mixing free energy of InMixing free energy of In GaGa N alloysN alloysMixing free energy of InMixing free energy of InxxGaGa11--xxN alloysN alloys
C itiComposition x
A. Tabata et al., Appl. Phys. Lett. A. Tabata et al., Appl. Phys. Lett. 8080, 769 (2002), 769 (2002)
Semiconductor Nanostructures
Alloy stabilization by biaxial strainAlloy stabilization by biaxial strainy yy y
A. Tabata et al., Appl. Phys. A. Tabata et al., Appl. Phys. Lett. Lett. 8080, 769 (2002), 769 (2002)
a)a) Unstrained cUnstrained c--InGaN alloys on cInGaN alloys on c--GaN(001) bufferGaN(001) buffer)) yy ( )( )b)b) Complete suppression of spinodal decomposition for T = TComplete suppression of spinodal decomposition for T = Tss
Semiconductor NanostructuresSemiconductor Nanostructures
Thermal mismatch: Wafer bending and cracksThermal mismatch: Wafer bending and cracksgg
30 µm Ge/Si(001)30 µm Ge/Si(001)
Semiconductor Nanostructures
Growth on patterned Si substratesGrowth on patterned Si substratesGrowth on patterned Si substratesGrowth on patterned Si substratesMicromachinedMicromachined Si pillarsSi pillars Ge coverage: 8 Ge coverage: 8 µµmm
C V Fal b et al ScienceC V Fal b et al Science 335335 1330 (2012)1330 (2012)
Semiconductor Nanostructures
C.V. Falub et al., Science C.V. Falub et al., Science 335335, 1330 (2012), 1330 (2012)
SelfSelf--limiting lateral growthlimiting lateral growthg gg g
C.V. Falub et al., Science C.V. Falub et al., Science 335335, 1330 (2012), 1330 (2012)
Semiconductor Nanostructures
Elastic relaxation of thermal strainElastic relaxation of thermal strainElastic relaxation of thermal strainElastic relaxation of thermal strain
Semiconductor Nanostructures
C.V. Falub et al., Science C.V. Falub et al., Science 335335, 1330 (2012), 1330 (2012)
Characterization of epitaxial nanostructuresCharacterization of epitaxial nanostructuresCharacterization of epitaxial nanostructuresCharacterization of epitaxial nanostructures
Structural:Structural:–– Reflection high energy electron diffraction (RHEED)Reflection high energy electron diffraction (RHEED)–– Optical reflection spectroscopyOptical reflection spectroscopy–– XX--ray diffractionray diffraction–– Transmission electron microscopyTransmission electron microscopy
Secondary ion mass spectrometry (SIMS)Secondary ion mass spectrometry (SIMS)–– Secondary ion mass spectrometry (SIMS)Secondary ion mass spectrometry (SIMS)–– Rutherford backscattering spectrometry (RBS)Rutherford backscattering spectrometry (RBS)
Optical:Optical:Optical:Optical:–– Reflection & transmissionReflection & transmission–– PhotoluminescencePhotoluminescence–– Raman scatteringRaman scattering
Electrical:Electrical:–– Conductivity & Hall effectConductivity & Hall effect
Semiconductor Nanostructures
Molecular beam epitaxyMolecular beam epitaxyMolecular beam epitaxyMolecular beam epitaxy
Semiconductor Nanostructures
RHEED pattern from a rectangular RHEED pattern from a rectangular p gp g22--D latticeD lattice
Semiconductor Nanostructures
Typical RHEED pattern (0Typical RHEED pattern (0thth Laue zone)Laue zone)Typical RHEED pattern (0Typical RHEED pattern (0thth Laue zone)Laue zone)
Semiconductor Nanostructures
RHEED pattern of Si(111)RHEED pattern of Si(111)--77××77RHEED pattern of Si(111)RHEED pattern of Si(111) 77 77
Incident electron beam along <11Incident electron beam along <11--2> azimuth2> azimuth
Semiconductor Nanostructures
Incident electron beam along <11Incident electron beam along <11 2> azimuth2> azimuth
Rough GaN layer on AlN bufferRough GaN layer on AlN bufferRough GaN layer on AlN bufferRough GaN layer on AlN buffer
Diffraction spots due to transmission through islandsDiffraction spots due to transmission through islands
Semiconductor Nanostructures
RHEED oscillations (schematic)RHEED oscillations (schematic)RHEED oscillations (schematic)RHEED oscillations (schematic)
Semiconductor Nanostructures
Coplanar highCoplanar high--angle xangle x--ray diffractionray diffractionCoplanar highCoplanar high--angle xangle x--ray diffractionray diffraction
Coplanar highCoplanar high--angle xangle x--ray diffractionray diffractionCoplanar highCoplanar high--angle xangle x--ray diffractionray diffraction
HRXRD analysis: 30 HRXRD analysis: 30 µµm Ge towers vs. continuous film m Ge towers vs. continuous film HRXRD analysis: 30 HRXRD analysis: 30 µµm Ge towers vs. continuous film m Ge towers vs. continuous film
Semiconductor NanostructuresC.V. Falub et al., Science C.V. Falub et al., Science 335335, 1330 (2012), 1330 (2012)
HRXRD analysis of 30 HRXRD analysis of 30 µµm Ge towers m Ge towers HRXRD analysis of 30 HRXRD analysis of 30 µµm Ge towers m Ge towers
Semiconductor NanostructuresC.V. Falub et al., Science C.V. Falub et al., Science 335335, 1330 (2012), 1330 (2012)
Strain state of cStrain state of c--GaN/InGaN/GaN(001)GaN/InGaN/GaN(001)/ / ( )/ / ( )
(a) d(a) dInGaNInGaN = 30 nm= 30 nm
Tabata et alTabata et alTabata et al.Tabata et al.
Appl. Phys. Lett. Appl. Phys. Lett. 8080, 769, 769
(2002)(2002)
(b) d(b) dInGaNInGaN = 3 nm= 3 nm
Semiconductor Nanostructures
Near band edge PL of alloysNear band edge PL of alloysea ba d edge o a oysea ba d edge o a oys
S. Chichibu, nature materials 5, 810 (2006)S. Chichibu, nature materials 5, 810 (2006)
Semiconductor Nanostructures
Periodic table of elementsPeriodic table of elementsPeriodic table of elementsPeriodic table of elements
Semiconductor Nanostructures
GaN PL intensity vs TDDGaN PL intensity vs TDDGaN PL intensity vs. TDDGaN PL intensity vs. TDD
Theory: J.H. You, J. Appl. Phys. Theory: J.H. You, J. Appl. Phys. 101101, 023516 (2007), 023516 (2007)
Semiconductor Nanostructures
y , pp yy , pp y , ( ), ( )
AlAl GaGa N/GaN heterostructureN/GaN heterostructureAlAl0.090.09GaGa0.910.91N/GaN heterostructureN/GaN heterostructure
Sheet electron density 2.12 Sheet electron density 2.12 ×× 10101212 cmcm--2 2 at 4 Kat 4 KMobility 60‘000 cmMobility 60‘000 cm22/Vs at 4 K/Vs at 4 K
C.R. Elsass et al., Jap. J. Appl. Phys. 39, L1023 (2000) C.R. Elsass et al., Jap. J. Appl. Phys. 39, L1023 (2000)
Semiconductor Nanostructures
Mobility limiting scattering mechanismsMobility limiting scattering mechanismsMobility limiting scattering mechanismsMobility limiting scattering mechanisms
Semiconductor Nanostructures
D. Jena et al., Am. Phys. Soc. March Meeting, Seattle, Washington, 2001D. Jena et al., Am. Phys. Soc. March Meeting, Seattle, Washington, 2001
Elementary processes in epitaxyElementary processes in epitaxyElementary processes in epitaxyElementary processes in epitaxy
Semiconductor Nanostructures
IIIIII V MBE at LV MBE at L NESS in ComoNESS in ComoIIIIII--V MBE at LV MBE at L--NESS in ComoNESS in Como
Semiconductor Nanostructures
Generic CVD systemGeneric CVD systemGeneric CVD systemGeneric CVD system
Semiconductor Nanostructures
Epitaxial SiGe growth by CVDEpitaxial SiGe growth by CVDEpitaxial SiGe growth by CVDEpitaxial SiGe growth by CVD
Semiconductor Nanostructures
Temperature dependence of CVD Temperature dependence of CVD growth ratesgrowth rates
Semiconductor Nanostructures
CVD growth rate for Si homoepitaxyCVD growth rate for Si homoepitaxyCVD growth rate for Si homoepitaxyCVD growth rate for Si homoepitaxy
E.C. Everstyn, Philips Research Rept. E.C. Everstyn, Philips Research Rept. 1919, 45 (1974), 45 (1974)
Semiconductor Nanostructures
Group III nitride MOCVDGroup III nitride MOCVDpp
Aixtron planetary reactorAixtron planetary reactorAixtron planetary reactorAixtron planetary reactor
Note numerous gas phase reactionsNote numerous gas phase reactions
M. Dauelsberg, M. Dauelsberg, ICMOVPE XIII, May ICMOVPE XIII, May 2222--26 26 2006, 2006, Miyazaki, JapanMiyazaki, Japan
Semiconductor Nanostructures
Deposition of SiGe by LEPECVDDeposition of SiGe by LEPECVD
200 mm LEPECVD200 mm LEPECVD200 mm LEPECVD200 mm LEPECVDsystemsystem
ArAr ArAr
SiSi++HH
HH ++
ArAr
ArArArArSiSi
HHHH
HHHH
ArArArArArAr
GeGeHHHH
HH++
HH ++
ArArGeGe
HHHH
HHHH
ArAr
SiSi GeGeGeGe SiSi SiSi SiSiGeGe
Principle of lowPrinciple of low--energy energy plasmaplasma--enhanced CVD:enhanced CVD:HighHigh--currentcurrent lowlow--voltage voltage arc dischargearc discharge HH++arc dischargearc dischargeSiHSiH44 and GeHand GeH44 are transformed are transformed into highly reactive radicalsinto highly reactive radicals
Very high growth rates (0 5Very high growth rates (0 5 µm/min)µm/min)Very high growth rates (0.5 Very high growth rates (0.5 µm/min) µm/min) possible at low substrate possible at low substrate temperaturestemperatures
Hydride vapor phaseHydride vapor phase epitaxyepitaxyHydride vapor phase Hydride vapor phase epitaxyepitaxy
Typical substrate temperatures 1000Typical substrate temperatures 1000--11001100ooCCGrowth rates of several 100 Growth rates of several 100 µm/hµm/h
Semiconductor Nanostructures