ABSTRACT
Among the currently developing technologies, the only three that take advantage of low-dimensional propertiesofquantummechanicsincludetype-IIInAs/GaSbsuperlattice(SL)photodetectors,the quantumwellintersubbandphotodetectors,andthequantumdotinfraredphotodetector.Goingby dimensionality,thetype-IIsuperlatticeisstillathree-dimensionalsystem,thesameasabulksemiconductor,whiletheothertwosystemsaresotospeak“two-andzero-dimensionalsystems,”respectively, meaningthattheconfinementsofcarriersarelocallyinoneormorethanonedirection.However,comparedwiththequantumwellandthequantumdot,type-IIsuperlatticessharethesamecapabilityof spatiallylocalizingelectronsinananoscalespace.™isisduetothespatialseparationofcarriersinthe constituentlayers.Moreover,thephysicsthatunderliethetype-IIsuperlatticegiveustheuniqueability
24.1 Introduction ....................................................................................24-1 24.2Material System and Variants of Type-II Superlattices ............24-2
24.3 Historic Development of Type-II Superlattice Photodetectors ................................................................................24-5
24.4Physics of Type-II InAs/GaSb Superlattice .................................24-7 24.5Material Growth and Characterization ......................................24-8 24.6Device Fabrication and Passivations .........................................24-11
Acknowledgment ......................................................................................24-29 References ..................................................................................................24-29
givesus,inthissystem,anadditionaldegreeoffreedomfordesigningandcreatingnew“materials.” ™isisnotunlikethewayNaturecreatedsolidcrystalsfromatoms.Havingbulk-likeproperties,type-II superlatticescanbeexploitedusingtheconsiderableunderstandingacquiredforbulksemiconductors inthepast.™isknowledgecanbeusedtooptimallydesigndevicearchitecturesforphotodetecting applications.™eclosematchbetweentheoreticalworkandexperimentaldevelopmentshasallowed type-IIsuperlatticephotodetectorstobecomeoneofthefastest-growingtechnologiesininfrareddetection.Duringadecadeofmaturing,thematerialsystemhasexperiencedsignificantprogressthathas li®edthedetectorperformancetonowhavecomparablelevelstothestate-of-the-artmercurycadmium telluride(MCT)technology.Whetherthesuperlatticeinfraredphotodetectorscanoutperformthebulk narrow-gapMCTdetectorsornotisoneofthemostimportantquestionsforthefutureoftheinfrared detection technology.
