MOCVD法制备ZnO：Ga透明导电薄膜及特性研究
摘要
ZnO作为一种新型的宽带隙半导体材料,在近年来受到越来越大的关注。ZnO具有良好的物理性质:直接带隙能带结构、室温禁带宽度3.37eV、激子束缚能60meV,具备了常温下高效发射紫外光的必要条件。作为蓝紫光发光二极管(LED)和紫外激光器(LD)有着广阔的发展前景,在表面声波器件、平面光波导,透明电极,紫外光探测器、压电器件、紫外发光器件、气敏传感器等领域有着很好的应用。
氧化锌薄膜的制备有很多方法,包括磁控溅射、脉冲激光沉积(PLD)、金属有机化学气相沉积(MOCVD)、分子束外延(MBE)、喷雾热分解、溶胶-凝胶法(sol-gel)等等。MOCVD方法因其成膜质量好,生长源量均匀可控,并能实现快速、大面积、多片同时生长,对ZnO薄膜的产业化有着重要的意义。
本文采用MOCVD方法制备出了Ga掺杂的ZnO透明导电薄膜,利用X射线衍射(XRD)、透射谱和霍尔效应测试,系统研究了MOCVD系统中的实验参数对ZnO:Ga的结构、光学和电学性质。具体研究内容如下:
(1)通过改变生长温度,研究了生长温度对ZnO:Ga薄膜结构、透过率及电学性质的影响。
(2)通过改变TMGa源流量,研究了Ga掺杂量对ZnO:Ga薄膜结构、透过率及电学性质的影响。
(3)研究了氧气流量对ZnO:Ga薄膜结构、透过率及电学性质的影响。
通过三步实验,在氧气流量为325sccm、TMGa流量为0.5sccm、生长温度为450℃时可以制备出了高透过率、低电阻率的ZnO透明导电薄膜,方块电阻最低达到18.280/sq,电阻率低于9.2×10~(-4)O·cm,可见光范围平均透过率80%以上。
As a new large gap semiconductor material, ZnO attracts more and more attentions in recent years. ZnO has large large direct band gap of 3.37eV, and large exciton binding energy of 60meV at room temperature which provides an attractive prospect to highly efficient UV light emitters, light emitting diodes (LEDs). ZnO thin film is used widely and effectively in the fields of surface acoustic wave devices, planar optical waveguides, transparent electrodes, ultraviolet photo-detectors, piezoelectric devices, UV light emitting diodes and laser diodes, gas sensors and so on.
There are many technique methods to be used to deposit ZnO films, such as magnetron sputtering, pulsed laser deposition(PLD), metal organic chemical vapor deposition(MOCVD), molecular beam epitaxy(MBE), spray pyrolysis and sol-gel process. MOCVD is of particular importance for producing high quality films over large areas in a manufacturing mode for it can prepare of high quality films, control uniform source volume and achieve rapid, large-area, multi-chip at the same time.
In this paper the Ga doped ZnO transparent conducting films was prepared by MOCVD. Studied the influence of experimental parameters on structure, electrical properties and transparent of the samples by X-ray diffraction, Hall effect, transmission spectra.
(1) Studied the influence of temperature on structure, electrical properties and transparent of the ZnO:Ga film.
(2) Studied the influence of TMGa flux on structure, electrical properties and transparent of the ZnO:Ga film.
(3) Studied the influence of oxygen flux on structure, electrical properties and transparent of the ZnO:Ga film.
high- transparence , low-resistivity ZnO transparent conductive film with average transmittance of 80%, sheet resistance of 18.28ohm/ cm~3 and resistivity lower than 9.2×10~(-4)O·cm can be achieved.
氧化锌薄膜的制备有很多方法,包括磁控溅射、脉冲激光沉积(PLD)、金属有机化学气相沉积(MOCVD)、分子束外延(MBE)、喷雾热分解、溶胶-凝胶法(sol-gel)等等。MOCVD方法因其成膜质量好,生长源量均匀可控,并能实现快速、大面积、多片同时生长,对ZnO薄膜的产业化有着重要的意义。
本文采用MOCVD方法制备出了Ga掺杂的ZnO透明导电薄膜,利用X射线衍射(XRD)、透射谱和霍尔效应测试,系统研究了MOCVD系统中的实验参数对ZnO:Ga的结构、光学和电学性质。具体研究内容如下:
(1)通过改变生长温度,研究了生长温度对ZnO:Ga薄膜结构、透过率及电学性质的影响。
(2)通过改变TMGa源流量,研究了Ga掺杂量对ZnO:Ga薄膜结构、透过率及电学性质的影响。
(3)研究了氧气流量对ZnO:Ga薄膜结构、透过率及电学性质的影响。
通过三步实验,在氧气流量为325sccm、TMGa流量为0.5sccm、生长温度为450℃时可以制备出了高透过率、低电阻率的ZnO透明导电薄膜,方块电阻最低达到18.280/sq,电阻率低于9.2×10~(-4)O·cm,可见光范围平均透过率80%以上。
As a new large gap semiconductor material, ZnO attracts more and more attentions in recent years. ZnO has large large direct band gap of 3.37eV, and large exciton binding energy of 60meV at room temperature which provides an attractive prospect to highly efficient UV light emitters, light emitting diodes (LEDs). ZnO thin film is used widely and effectively in the fields of surface acoustic wave devices, planar optical waveguides, transparent electrodes, ultraviolet photo-detectors, piezoelectric devices, UV light emitting diodes and laser diodes, gas sensors and so on.
There are many technique methods to be used to deposit ZnO films, such as magnetron sputtering, pulsed laser deposition(PLD), metal organic chemical vapor deposition(MOCVD), molecular beam epitaxy(MBE), spray pyrolysis and sol-gel process. MOCVD is of particular importance for producing high quality films over large areas in a manufacturing mode for it can prepare of high quality films, control uniform source volume and achieve rapid, large-area, multi-chip at the same time.
In this paper the Ga doped ZnO transparent conducting films was prepared by MOCVD. Studied the influence of experimental parameters on structure, electrical properties and transparent of the samples by X-ray diffraction, Hall effect, transmission spectra.
(1) Studied the influence of temperature on structure, electrical properties and transparent of the ZnO:Ga film.
(2) Studied the influence of TMGa flux on structure, electrical properties and transparent of the ZnO:Ga film.
(3) Studied the influence of oxygen flux on structure, electrical properties and transparent of the ZnO:Ga film.
high- transparence , low-resistivity ZnO transparent conductive film with average transmittance of 80%, sheet resistance of 18.28ohm/ cm~3 and resistivity lower than 9.2×10~(-4)O·cm can be achieved.
引文
[1]M.H.Koch,A.J.Hartmann,R.N.Lamb,et al.Self-Texture in the initial stages of ZnO film growth.J.Phys.Chem.B,1997,101(4),p8231.
[2]梁红伟.高质量氧化锌薄膜和低维结构的制备及研究:(博士毕业论文).长春:长春光学精密机械与物理所,2005.
[3]H.S.Ku,H.Takashi,K.H.Ju,et al.Control of polarity of ZnO films grown by plasma-assisted molecular-beam epitaxy:Zn-and O-polar ZnO films on Ga-palor GaN templates.Appl.Phys.Lett.2000,77(22):3571-3573.
[4]D.G.Thomas.The exciton spectrum of zinc oxide,J.Phys.Chem.Solids,1960,15:86-96.
[5]J.J.Hopfield.Fine structure in the optical absorption edge of anisotropiccrystals.J.Phys.Chem.Solids,1960,15:97-107.
[6]Y.S.Park,C.W.Litton,T.C.Collins,and D.C.Reynolds.Exciton Spectrum of ZnO.Phys.Rev.1966,143:512-519.
[7]D.C.Reyno]ds,D.C.Look,B.Jogai,C.Litton,G.CantWell,W.Harsch.Valence-band ordering in ZnO.Phy.Rev.B.1999,60:2340-2344.
[8]Y.Tajahashi,Kanamori M,et al.ZnO-SnO_2 transparent conductive films deposited by opposed target sputtering system of ZnO and SnO_2 targets.Vacuum 2004;74:607-611.
[9]张源涛.ZnO薄膜和MgZnO合金薄膜的生长及其特性研究:(博士毕业论文).长春:吉林大学,2005
[10]Y.Tajahashi,Kanamori M,Kondoh A,et al.Photoconductivity of ultrathin zinc oxide films.Jpn J hppl Phys,1994,33:6611
[11]D.H.Zhang,D.E.Brodie,Photoresponse of polycrystalline ZnO films deposited by RF bias sputtering,Thin Solid Films,1995,261:334
[12]D.H.Zhang.Fast photoresponse and the related change of crystallite barriers for ZnO films deposited by RF sputtering.J Phys D,1995,28:1273
[13]H.fabricius,T.Skettrup,P.Bisgaard.Ultraviolet detectors in thin sputtered ZnO films.Appl Optics,1986,25:2764
[14]S.Liang,H.Sheng,Y.Liu,et al.ZnO Schottky ultraviolet photodetectors,J Cryst Growth,2001,225:110-113.
[15]马勇.ZnO薄膜制备及性质研究:(博士毕业论文).重庆:重庆大学,2004.
[16]T.Aoki,Y.Hatanaka,D.C.Look.ZnO diode fabricated by excimer-laser doping.Appl.Phys.Lett.2000,76:3257-3259.
[17]Y.R.Ryu,S.Zhu,D.C.Look,Synthesis of p-type ZnO films.J.Crystal Growth.2000,216:330-334.
[18]Y.R.Ryu,T.S.Lee,J.H.Leem,et al.Appl.Phys.Lett.2003,83:4032-4034.
[19]Y.I.Alivov,E.V.Kalinina,A.E.Cherenkov,et al.Fabrication and characterization of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates.Appl.Phys.Lett 2003,83:4719-4721.
[20]A.Tsukazaki,A.Ohtomo,T.Onuma,et al.Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO.Nature Materials,2004,4:42-46.
[21]Takayuki Makino.Optical properties of ZnO-based quantum structures.Superlattices and Microstructures.2005,38-231-244.
[22]李世涛,乔学亮,陈建国.透明导电薄膜的研究现状及应用.激光与光电子学进展[J].2003年7月.Vol40,No.7.
[23]王金库,陈军,林薇薇透.明导电聚苯胺复合膜的研究进展.材料科学与工程,2001,19:121-124.
[24]王慧,刘静.透明导电薄膜概述.陶瓷[J].2007.No.12:12-17.
[25]Samson James.A R,Techniques of vacuum ultraviolet spectroscopy[M].New York:John Wiley & Sons.Inc.1967.
[26]Gilbert I,Freer R.Donor and acceptor doping of zinc oxide varistors.J Phys:Condens Matter,2002,14:945.
[27]N.Roberts,R.P.Wang,A.W.Sleight,et al.Phys.Rev.B57(1998)5734.
[28]J.D.Ye,S.L.Gu,S.M.Zhu,et al.Gallium doping dependence of single-crystal n-type Zno grown by metal organic chemical vapor deposition.Journal of Crystal Growth 283(2005)279-285
[29]B.J.Jin,S.H.Bae,S.Y.Lee.Effects of native defects on optical and electrical properties of ZnO prepared by pulsed laser deposition.Mater.Sci.Eng.B,2000,71:301-305.
[30]John.F.Wager.Transparent Electronics.Science 300,1245(2003).
[31]E.Burstein,Anomalous Optical Absorption Limit in InSb.Phy.Rev.93(1954)632.
[32]沈学础.半导体光学性质.北京:科学出版社,1992.
[33]吴自勤,王兵.薄膜生长,北京:科学出版社,2001
[34]方容川.固体光谱学.合肥:中国科学技术大学出版社,2001.
[35]沈学础.半导体光学性质.北京:科学出版社,2003.
[36]刘维峰.ZnO:Al透明导电薄膜和ZnO发光器件的制备及特性研究:(博士毕业论文).大连:大连理工大学,2006.
[37]Kang H S,Kang J S,Kim J W,et al.Annealing effect on the property of ultraviolet and green emissions of ZnO thin films.J Appl Phys.2004,95(3):1246-1250.
[38]张源涛.ZnO薄膜和MgZnO合金薄膜的生长及其特性研究:(博士毕业论文).长春:吉林大学,2005
[39]崔勇国.采用MOCVD方法在Si和GaAs衬底上生长ZnO薄膜及其特性研究.博士论文.吉林大学2006.6
[2]梁红伟.高质量氧化锌薄膜和低维结构的制备及研究:(博士毕业论文).长春:长春光学精密机械与物理所,2005.
[3]H.S.Ku,H.Takashi,K.H.Ju,et al.Control of polarity of ZnO films grown by plasma-assisted molecular-beam epitaxy:Zn-and O-polar ZnO films on Ga-palor GaN templates.Appl.Phys.Lett.2000,77(22):3571-3573.
[4]D.G.Thomas.The exciton spectrum of zinc oxide,J.Phys.Chem.Solids,1960,15:86-96.
[5]J.J.Hopfield.Fine structure in the optical absorption edge of anisotropiccrystals.J.Phys.Chem.Solids,1960,15:97-107.
[6]Y.S.Park,C.W.Litton,T.C.Collins,and D.C.Reynolds.Exciton Spectrum of ZnO.Phys.Rev.1966,143:512-519.
[7]D.C.Reyno]ds,D.C.Look,B.Jogai,C.Litton,G.CantWell,W.Harsch.Valence-band ordering in ZnO.Phy.Rev.B.1999,60:2340-2344.
[8]Y.Tajahashi,Kanamori M,et al.ZnO-SnO_2 transparent conductive films deposited by opposed target sputtering system of ZnO and SnO_2 targets.Vacuum 2004;74:607-611.
[9]张源涛.ZnO薄膜和MgZnO合金薄膜的生长及其特性研究:(博士毕业论文).长春:吉林大学,2005
[10]Y.Tajahashi,Kanamori M,Kondoh A,et al.Photoconductivity of ultrathin zinc oxide films.Jpn J hppl Phys,1994,33:6611
[11]D.H.Zhang,D.E.Brodie,Photoresponse of polycrystalline ZnO films deposited by RF bias sputtering,Thin Solid Films,1995,261:334
[12]D.H.Zhang.Fast photoresponse and the related change of crystallite barriers for ZnO films deposited by RF sputtering.J Phys D,1995,28:1273
[13]H.fabricius,T.Skettrup,P.Bisgaard.Ultraviolet detectors in thin sputtered ZnO films.Appl Optics,1986,25:2764
[14]S.Liang,H.Sheng,Y.Liu,et al.ZnO Schottky ultraviolet photodetectors,J Cryst Growth,2001,225:110-113.
[15]马勇.ZnO薄膜制备及性质研究:(博士毕业论文).重庆:重庆大学,2004.
[16]T.Aoki,Y.Hatanaka,D.C.Look.ZnO diode fabricated by excimer-laser doping.Appl.Phys.Lett.2000,76:3257-3259.
[17]Y.R.Ryu,S.Zhu,D.C.Look,Synthesis of p-type ZnO films.J.Crystal Growth.2000,216:330-334.
[18]Y.R.Ryu,T.S.Lee,J.H.Leem,et al.Appl.Phys.Lett.2003,83:4032-4034.
[19]Y.I.Alivov,E.V.Kalinina,A.E.Cherenkov,et al.Fabrication and characterization of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates.Appl.Phys.Lett 2003,83:4719-4721.
[20]A.Tsukazaki,A.Ohtomo,T.Onuma,et al.Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO.Nature Materials,2004,4:42-46.
[21]Takayuki Makino.Optical properties of ZnO-based quantum structures.Superlattices and Microstructures.2005,38-231-244.
[22]李世涛,乔学亮,陈建国.透明导电薄膜的研究现状及应用.激光与光电子学进展[J].2003年7月.Vol40,No.7.
[23]王金库,陈军,林薇薇透.明导电聚苯胺复合膜的研究进展.材料科学与工程,2001,19:121-124.
[24]王慧,刘静.透明导电薄膜概述.陶瓷[J].2007.No.12:12-17.
[25]Samson James.A R,Techniques of vacuum ultraviolet spectroscopy[M].New York:John Wiley & Sons.Inc.1967.
[26]Gilbert I,Freer R.Donor and acceptor doping of zinc oxide varistors.J Phys:Condens Matter,2002,14:945.
[27]N.Roberts,R.P.Wang,A.W.Sleight,et al.Phys.Rev.B57(1998)5734.
[28]J.D.Ye,S.L.Gu,S.M.Zhu,et al.Gallium doping dependence of single-crystal n-type Zno grown by metal organic chemical vapor deposition.Journal of Crystal Growth 283(2005)279-285
[29]B.J.Jin,S.H.Bae,S.Y.Lee.Effects of native defects on optical and electrical properties of ZnO prepared by pulsed laser deposition.Mater.Sci.Eng.B,2000,71:301-305.
[30]John.F.Wager.Transparent Electronics.Science 300,1245(2003).
[31]E.Burstein,Anomalous Optical Absorption Limit in InSb.Phy.Rev.93(1954)632.
[32]沈学础.半导体光学性质.北京:科学出版社,1992.
[33]吴自勤,王兵.薄膜生长,北京:科学出版社,2001
[34]方容川.固体光谱学.合肥:中国科学技术大学出版社,2001.
[35]沈学础.半导体光学性质.北京:科学出版社,2003.
[36]刘维峰.ZnO:Al透明导电薄膜和ZnO发光器件的制备及特性研究:(博士毕业论文).大连:大连理工大学,2006.
[37]Kang H S,Kang J S,Kim J W,et al.Annealing effect on the property of ultraviolet and green emissions of ZnO thin films.J Appl Phys.2004,95(3):1246-1250.
[38]张源涛.ZnO薄膜和MgZnO合金薄膜的生长及其特性研究:(博士毕业论文).长春:吉林大学,2005
[39]崔勇国.采用MOCVD方法在Si和GaAs衬底上生长ZnO薄膜及其特性研究.博士论文.吉林大学2006.6