应变GaN量子点中激子态的研究(英文)-豆柴文库

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应变GaN量子点中激子态的研究(英文)
InvestigationofExcitonStatesinStrainedGaNQuantumDots
Introduction:
GaNquantumdots(QDs)havedrawnsignificantattentionrecentlyduetotheiruniquepropertiessuchaslargeexcitonbindingenergy,highluminescenceefficiency,andexcellentthermalstability.Byapplyinganexternalstrain,thebandstructureofGaNQDscanbemodified,leadingtochangesintheiropticalandelectronicproperties.Inthispaper,weperformedathoroughinvestigationoftheexcitonstatesinstrainedGaNQDs.
Methods:
Weuseddensityfunctionaltheory(DFT)calculationstostudytheelectronicpropertiesofGaNQDsunderstrain.ThesimulationwasperformedusingtheViennaAbinitioSimulationPackage(VASP),whichisbasedonaplane-wavebasissetandprojectoraugmentedwave(PAW)method.Theexchange-correlationpotentialwasdescribedusingthePerdew-Burke-Ernzerhof(PBE)functional.
Results:
WefirststudiedtheelectronicbandstructureoftheunstrainedGaNQD.AttheГpoint,thehighestvalencebandisdominatedbytheporbitalofNatomsandthelowestconductionbandiscomposedofsandporbitalsofGaatoms.Wethenappliedin-planetensilestrainstotheGaNQDandstudiedtheeffectontheelectronicbandstructure.Wefoundthatforstrainsbetween0%and2%,theenergygapbetweenthehighestvalencebandandthelowestconductionbandincreasedlinearlywithstrain.Above2%strain,theenergygapstartedtosaturate.Thisbehaviorisconsistentwiththephenomenonofquantumconfinement.
Next,weinvestigatedtheexcitonstatesoftheGaNQD.Excitonsarestronglycorrelatedelectron-holepairs,andduetoquantumconfinement,theycanbetightlyconfinedintheGaNQD.WecalculatedtheexcitonbindingenergybyapplyingtheBethe-Salpeterequation(BSE)method.Wefoundthat,underunstrainedconditions,thebindingenergyoftheexcitonwasaround20meV.However,under2%tensilestrain,thebindingenergywasincreasedtoabout30meV.ThisincreaseinbindingenergyisduetothereductionoftheexcitonBohrradiuscausedbythestrain.
DiscussionandConclusion:
Inthisstudy,wehaveinvestigatedtheelectronicandexcitonpropertiesofstrainedGaNQDs.Wefoundthattheelectronicbandgapincreasedlinearlywithstrain,andtheexcitonbindingenergywasenhanceddue