Charge Carrier Transport and Electromagnetic Properties of Monolayer ⅢA-nitrides Studied by First-principles

Author:Tong Li Jia

Supervisor:chen zuo

Database:Doctor

Degree Year:2018

Download:3

Pages:145

Size:9802K

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Low-dimension materials materials promote the development of nanoelectronic devices(such as field-effect transistor and nano-spin-electronic devices).Developing high-performance nano field-effect transistor(FET)requires two-dimensional(2D)materials with usable carrier mobility,proper bandgap and well thermodynamic stability(in the air).Assembling nano-spin-electronic devices requires one-dimensional(2D)materials with tunable electromagnetic properties.Pristine(1L-BN,1L-AlN and 1L-GAN)and fully-functionalizated 2D monolayer ⅢA nitrides possess large bandgap and excellent thermal stability.However,to date,it isn’t clear that monolayer ⅢA nitride have usable carrier mobility.Therefore,in the present work,we carried out first principles calculation using Vienna Ab-initio Simulation Package(VASP)to investigate the carrier mobilities of pristine(1L-BN,1L-AlN and 1L-GAN)and fully-functionalizated 2D monolayer ⅢA nitrides.In addition,the electromagnetic properties of ⅢA nitride zigzag nanoribbons(ZBNNR,ZAlNNR and ZGaNNR)are also calculated to explore how fully-hydrogenation and single C-chain doping affects the electromagnetic properties of ⅢA nitride zigzag nanoribbons.Pristine 2D monolayer ⅢA nitrides(1L-BN,1L-AlN and 1L-GaN)show a hole-dominated ultra-large carrier mobility,and their hole mobilities(12075277 cm2V-1s-1)are super to that of commercial silicon-based devices(500 cm2V-1s-1).Among these pristine2D monolayer ⅢA nitrides,1L-AlN shows the highest hole mobility(5277 cm2V-1s-1),1L-GaN shows the lowest hole mobility(1207 cm2V-1s-1),and 1L-BN possesses a moderate hole mobility:2026-2055 cm2V-1s-1.Synchronously,the electron mobilities of 1L-AlN and1L-GaN(425-457 cm2V-1s-1)are higher than that of 1L-BN(166 cm2V-1s-1)and are comparable to that of commercial silicon-based devices(500 cm2V-1s-1).In addition,the electron mobilities of pristine 2D monolayer ⅢA nitrides(1L-BN,1L-AlN and 1L-GaN)are anisotropic.On the contrary,their hole mobilities(especially 1L-AlN)are isotropic.Fully-functionalization can reverse the polarity of the carrier mobility of pristine 2D monolayer ⅢA nitrides(1L-BN,1L-AlN and 1L-GaN).Specially,fully-functionalization can suppress the hole mobilities of pristine 2D monolayer ⅢA nitrides and can even decrease the hole mobilities of fully-hydrofluorinated 1L-BN(FBNH)and fully-hydrogenated 1L-GaN(HGaNH)close to zero(less than 7 cm2V-1s-1).In contrast,fully-functionalization can enhance the electron mobilities of pristine 2D monolayer ⅢA nitrides.At last,the enhanced electron mobility and the depressed hole mobility reverse the polarity of carrier mobility,i.e.,the polarity of carrier mobility of pristine 2D monolayer ⅢA nitrides is reversed from hole-dominated to electron-dominated upon fully-functionalization.In addition,fully-functionalization(hydrogenation and hydrofluorination)can modulate the anisotropy(isotropy)of carrier mobility.Specially,the carrier mobilities of fully-hydrogenated 1L-BN(HBNH)and fully-functionalizated 1L-GaN(HGaNH and FGaNH)are anisotropic,while the carrier mobilities of fully-hydrogenated 1L-AlN(HAlNH)are isotropic.Pristine zigzag ⅢA nitrides nanoribbons(ZBNNR,ZAlNNR and ZGaNNR)are indirect-bandgap semiconductors.The increasing of the width of pristine zigzag ⅢA nitrides nanoribbons can modulate the charge density of the conduction-band-minimum(CBM)and valence-band-maximum(VBM),which induce their bandgap decreased with the increasing of the width of zigzag nanoribbons.In addition,the flat band states,which stems form the pz orbitals of righ-edge N atoms,also emerge in prinstine zigzag ⅢA nitrides nanoribbons.For zigzag ⅢA nitrides nanoribbons,the structure transformation from planar hexagonal structures to buckled configuration upon fully-hydrogenation are accompanied by a semiconductor-to-magnetic metal transition.The magnetism of fully-hydrogenated ZBNNR,ZAlNNR and ZGaNNR derive from the left-edge H or N atoms.And their magnetism decreased with the increasing of the width of zigzag nanoribbons.In addtion,single C-chain doping enables us to significant modulate the bandgap characteristic(means direct or indirect)of zigzag BN and AlN nanoribbons.For both of them,the left edge single C-chain doped ones possess the smallest bandgap due to theπbonds in their CBM.What’s more,the flat band states in zigzag AlN nanoribbons can be suppressed by single C-chain doping,and single C-chain doping also enables us to significant modulate the border states(stem fromπandπ*bonds)of zigzag AlN nanoribbons.