Cov cab kuj yog cov khoom uas muaj cov nqi hluav taws xob thiab tuaj yeem txav mus rau thauj tam sim no; piv txwv xws li electrons thiab ions. Semiconductors muaj ob hom kev thauj khoom: Tsis zoo them dawb electrons thiab qhov zoo them dawb qhov. Raws li cov neeg nqa khoom feem ntau, cov khoom siv hluav taws xob tau faib ua p- hom (qhov twg yog cov neeg nqa khoom feem ntau) lossis n- hom (qhov twg electrons yog cov neeg nqa khoom feem ntau). Hauv kev muaj tiag, lub qhov tsuas yog qhov chaw nyob hauv daim ntawv cog lus valence; qhov kev txav ntawm ib qho chaw tsis txaus yog sib npaug rau kev sib koom ua ke ntawm ntau tus valence electrons. Txawm li cas los xij, nws yog qhov yooj yim dua los piav qhia txog cov lus tsa suab ntawm qhov loj ntawm valence electrons siv lub tswv yim ntawm cov qhov me me. Yog li, hauv paus ntsiab lus, lub qhov tsuas yog lwm txoj hauv kev los sawv cev rau pawg loj ntawm valence electrons.
Lub zog lub xeev ntawm tus nqi thauj khoom
Los ntawm qhov kev xav ntawm lub zog siv lead ua bands, qhov siab tshaj plaws - lub zog hluav taws xob hauv ib qho khoom siv hluav taws xob yog cov khoom siv hluav taws xob thiab cov valence band, sib cais los ntawm qhov txwv tsis pub (lossis band sib txawv). Cov pawg txwv txwv tsis pub muaj lub xeev- lossis qib zog- cuam tshuam nrog delocalized motion, txawm hais tias lub zog hauv cheeb tsam uas tshwm sim los ntawm impurities lossis tsis xws luag yuav muaj nyob hauv nws. Dawb electrons (xws li yooj yim li electrons) nyob rau hauv lub conduction band, feem ntau nyob ze ntawm lub conduction band ntug (uas sib xws rau lub peev xwm ntawm lub electrons); dawb qhov (xws li yooj yim li qhov) nyob rau hauv lub valence band, feem ntau nyob ze ntawm lub valence band ntug (uas sib xws rau lub peev xwm ntawm lub qhov). Txawm hais tias lub valence band muaj ntau ntawm valence electrons, cov electrons no tau khi rau hauv valence bonds thiab tsis tuaj yeem txav mus los; yog li ntawd, lawv tsis raug cais raws li tus nqi thauj khoom.
Yog hais tias tus pub concentration nyob rau hauv ib tug n- hom semiconductor kuj tsawg, lub electron concentration nyob rau hauv conduction band tseem tsawg. Nyob rau hauv cov ntaub ntawv no, kev faib ntawm electrons nyob rau hauv lub zog theem nyob ze ntawm lub conduction band ntug raws li classical Boltzmann faib; cov electrons no yog hu ua non-degenerate carriers, thiab semiconductor yog cais raws li ib tug non-degenerate semiconductor.
Hloov pauv, yog tias qhov doping concentration yog siab heev, qhov kev faib tawm ntawm cov hluav taws xob ntau nyob ze ntawm qhov kev coj ua band ntug yog txwv los ntawm Pauli txoj cai tsis suav nrog. Hauv qhov xwm txheej no, cov hluav taws xob ua raws li quantum Fermi-Dirac faib; Lawv hu ua degenerate cov cab kuj, thiab cov semiconductor yog cais raws li ib tug degenerate semiconductor. Txawm li cas los xij, nws yuav tsum tau muab sau tseg tias txawm nyob rau hauv ib tug tsis yog -degenerate n- hom semiconductor, cov electrons nyob rau hauv lub valence band- ua ntau heev- tseem degenerate cov cab kuj thiab invariably ua raws li quantum Fermi - Dirac faib.
Lub qhov yog tsim thaum valence electrons hloov ntawm lub valence band mus rau lub conduction band (tawm tom qab vacancy nyob rau hauv lub valence bonds); cov txheej txheem no yog hu ua intrinsic excitation thiab yog tus yam ntxwv los ntawm lub simultaneous tiam ntawm electron -qhov khub.
