9781420038903%2Ech18

《9781420038903%2Ech18》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、18Phonon-DragThermopowerofLow-DimensionalSemiconductorStructures18.1Herring’sPhonon-Drag:BasicEquations....................18-118.2ThermopowerofDegenerate2DElectronGasatLowTemperatures.....................................................18-418.3ThermopowerofNondegenerate2DElectronGas....

2、18-718.4Two-StageDraginLow-DimensionalStructures.......18-8Yu.V.Ivanov18.5Phonon-DragThermoelectricFigure-of-Merit...........18-11IoffePhysical-TechnicalInstituteoftheRussianAcademyofSciencesAppendix18ARelaxationTimes...............................................18-1318.1Herring’sPhonon

3、-Drag:BasicEquationsInthree-dimensionalsemiconductorstheenergyandmomentumconservationconditionsrestrictthe1phasevolumeofphononsinteractingwithchargecarriers.Theelectronwithawavevectorkcanbescatteredonlybyaphononwhosewavevectorqhasalengthq&2k.Inlow-dimensionalstructuresthecomponentofanele

4、ctronwavevectoralongtheconfinementdirectionk’isnotdefined.Accordingtotheuncertaintyprinciple,Dk’,1=a;whereaisthecharacteristicsizeofaquantumwelloraquantumwire.Therefore,instructureswithnarrowquantumwellsthegivenrestrictiononthelengthofaphononwavevectorisremovedandthephasevolumeof“electroni

5、c”phonons,thoseinteractingwithcharge2,3carriers,sharplyincreases.Theriseinthephasevolumeofelectronicphonons(EP)resultsinamultipleincreaseinthephonon-dragthermopower.Thismechanismofthermopowerenhancementin4low-dimensionalstructuresappearstobefirststudiedbyKovarskiy.Inthischapterthefundamen

6、talsofelectron–phonon-draginlow-dimensionalstructuresisexamined.Attentionisfocusedonthequalitativedescriptionofphysicalprocesseswithinaframeworkofthesimplestmodelofanelectron–phononsystem.Itisassumedthatelectronsareconfinedinrectangularquantumwellswithinfinitelyhighpotentialbarriers.Thewid

7、thofquantumwellsissufficientlysmall,andthereforeonlythelowestsubbandoftheisotropicparabolicspectrumofcarriersisoccupied.Acousticphononsarethree-dimensionalandthespectrumisotropicandlinear.Theelectronsarescatteredbyunscreeneddeformationpotentialofacousticphonons.18-1©2006by