ihomogeneous contact potential mage of algan-grown sapphire substrate measured by kelvin probe force microscopy用探针力显微镜测量蓝宝石衬底上生长Algan GaN非均匀接触电位图.pdfVIP

Jpn.J.Appl.Phys.Vol.40(2001)pp.L589–L591

Part2,No.6B,15June2001

2001TheJapanSocietyofAppliedPhysicsc

InhomogeneousContactPotentialImageofAlGaN/GaNGrownonSapphireSubstrate

MeasuredbyKelvinProbeForceMicroscopy

YasuyukiEGUCHI,ShigeruKISHIMOTOandTakashiMIZUTANI

DepartmentofQuantumEngineering,NagoyaUniversity,Furo-cho,Chikusa-ku,Nagoya464-8603,Japan

(ReceivedApril19,2001;acceptedforpublicationApril25,2001)

ThecontactpotentialofAlGaN/GaNonsapphiresubstrategrownbymetalorganicchemicalvapordeposition(MOCVD)was

measuredbyKelvinprobeforcemicroscopy(KFM).Aclearcorrelationwasobservedbetweenthetopographicimageandthe

contactpotentialimage.Thepotentialaroundthesurfacepitswasabout100mVlowerthanthatinthesurroundingregion.

Thissuggeststheexistenceofaneffectofthepitsontheelectricalpropertiesoftheepitaxiallayer.Eventhoughthediameters

ofthepitswere20–60nm,thediameteroftheaffectedlow-potentialregionwasaslargeas0.3–0.7µm.

KEYWORDS:AlGaN/GaN,KFM,contactpotential,pits

GaN-baseddeviceshaveattractedconsiderableattention

becauseoftheirpotentialforblue-light-emittingdevicesand

high-powerelectrondevices.However,thesignificantdif-

ferencesinthelatticeparameterandthethermalexpansion

coefficientbetweenGaNandsapphire/SiC,whichhavebeen

commonlyusedforsubstrates,typicallyleadtothreadingdis-

locationswithadensityof1089−2

–10cm.Itisveryimportant

tostudytheeffectofdefectsonthestructural,opticaland

electronicpropertiesinordertodeveloptheirfullpotential

effectively.Eventhoughtherearemanyreportsontheoptical

propertiesofGaN,1–3)therearefewreportsonstudiesinves-

tigatingtheeffectsofdefectsontheelectricalpropertiesof

theGaNepitaxiallayermicroscopicallyinanondestructive

manner.Recently,scanningcapacitancemicroscopy(SCM)

hasrevealedthepresenceofnegativechargeinthevicinityof

dislocations.4)Theobtainedcapacitanceimagehadcorrela-

tionwiththedislocations.Improvementinthemeasurement

techniquewillhelpustodiscusstheef