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First-principles Investigation Of Electronic Structure Properties Of Two-dimensional Ingan Semiconductor Alloys

Posted on:2020-10-17Degree:MasterType:Thesis
Country:ChinaCandidate:Z Q WuFull Text:PDF
GTID:2428330596979613Subject:Physical Electronics
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Since the successful synthesis of graphene,two-dimensional(2D)materials have attracted tremendous attention due to their novel electronic,optical,thermal,and mechanical properties for potential applications in various fields,The quantum parameter nement effect and reduced shielding e in two-dimensional materials are often different from those in bulk materials,so they are being studied deeply.The gapless nature of graphene and low carrier mobility of transition-metal dichalcogenides,however,present limitations to their potential application in industry.Very recently,Balushi et al.were synthesized by migration enhancement encapsulation technique.When the surface suspension bond is passivated,the two-dimensional gan can be stabilized by bending structure under environmental conditions.The band gap of buckled 2D GaN is thickness-dependent,varying from 3.4 eV in the bulk to 5.0 eV in a monolayer limit.In recent decades,remarkable progress has been made in the development of optoelectronic devices based on III nitride such as AlN,GaN,InN and its alloys.In particular,the band gap values of INx GA1-x N alloys can vary around 0.7 eV(InN)to 3.5 eV(GaN)has direct band gap at room temperature,and its emission spectrum ranges from ultraviolet to near infrared,Howeverdue to the large lattice mismatch(10%)between Bulk-Inn and GaN,phase separation was observed in a wide range of compositions.Then,an interesting question naturally arises:What will be different in alloy properties when In.Gag-,N fi.lms are thinned to a few atomic layers?Using first-principles calculations based on density functional theory combined with a semi-empirical van der Waals dispersion correctiocn,we first investigated structural parameters,formation energy and band gap of of buckled and planar fe,w-layer GaN and InN.It is found that the lattice constant of two-dimensional InN is more sensitive than the lattice constant of GaN.The independent two-dimensional GaN and InN with planar structure are stable with indirect band gap character.In contrast,the two-dimensional GaN and InN materials of the buckled structure which is passivated by hydrogen atoms are more stable than the two-dimensional GaN and InN materials of the planar structure,and have direct gap character.Furthermore,the stability of the two-dimensional nitride semiconductor decreases as the thickness of the film decreases.Then,we study the structural parameters,mixing layer and band gap of the buckling and the difference layer xgal-xn alloy.We predict that the band gap of InxGa1-xN alloy with hydrogen passivation can be tuned from 5.6 eV to 0.7 eV,retaining the direct bandgap and clear Bloch characteristics,make it an ideal candidate for future luminescence applications.Unlike their ontology,in these two-dimensional systems,phase separation can be suppressed due to the reduction of geometric constraints.The disordered planar thin films have serious lattice distortion and almost lose the Bloch property of valence band,while the ordered planar films maintain the Bloch property,but the mixing enthalpy is the highest.
Keywords/Search Tags:First principle, InGaN alloy, electronic structure, mixing enthalpies
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