Si_Ge nanostructures_yy174_2002.pdf

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1、INSTITUTEOFPHYSICSPUBLISHINGREPORTSONPROGRESSINPHYSICSRep.Prog.Phys.65(2002)2772PII:S0034-4885(02)93942-4Si/GenanostructuresKarlBrunnerWalterSchottkyInstitut,TechnischeUniversitatM¨unchen,AmCoulombwall,¨D-85748Garching,GermanyE-mail:brunner@wsi.tum.deReceived10August2001,infinalform2O

2、ctober2001Published12December2001Onlineatstacks.iop.org/RoPP/65/27AbstractAreviewisgivenontheformationmechanismsandthepropertiesofSi/Genanostructuresthathavebeensynthesizedbyself-assemblingandself-orderingduringheteroepitaxyofsilicongermaniumalloysonsingle-crystalsiliconsubstrates.Th

3、epropertiesofelectronicsubbandsinsmoothstrainedSi/SiGequantumwellstructuresarepresentedasabasisforcharacterizingcoherentSi/Genanostructureswithfreemotionofcarriersinareducednumberofdimensions.Thelow-dimensionalbandstructureofvalencebandstatesconfinedinstrainedSi/GeandSi/SiGenanostruct

4、uresisanalysedbyopticalandelectricalspectroscopy.Thenanostructurespresentedwerefabricatedbyself-assemblyinducedbyelasticstrainrelaxationwithoutapplyinganypatterningtechnique.MisfitlatticestrainofSiGematerialdepositedonSisubstratescanrelaxbybunchingofatomicsurfacestepswithSiGeagglomera

5、tionatthestepedgesorbynucleationofGe-richislandsintheStranskiKrastanowgrowthmode.Thesize,densityandcompositionofsuchSi/Genanostructuresrepresentingquantumwiresanddots,respectively,canbetunedinawiderangebythegrowthparameters.LocalstrainfieldsextendingintotheSihostinfluencethenucleationa

6、ndthelateralarrangementofnanostructuresinsubsequentlayersandcanbeappliedforself-orderingofnanostructuresintheverticalaswellasthelateraldirection.Interbandandintra-valence-bandphotocurrent,absorptionandphotoluminescencespectroscopyaswellasCVandadmittancemeasurementsrevealaconsistentvi

7、ewofthebandstructureinSi/Gequantumdotstructures.Thisisingoodagreementwithmodelcalculationsbasedonbandoffsets,deformationpotentialsandeffectiveelectronmassesknownfromearlierstudiesofSi/SiGequantumwellstructures.TheeffectivevalencebandoffsetsofholestateswithinSi/Genanostructuresreachab

8、out400meV.Ty