【作者】 栾彩娜；

【导师】 马瑾；

【作者基本信息】 山东大学 ， 微电子学与固体电子学， 2012， 博士

【摘要】 随着第三代半导体材料的发展,宽带隙氧化物半导体材料成为人们关注的焦点和热点。宽带隙氧化物半导体材料是制备透明及紫外光电子器件的非常具有潜力的重要材料,极具开发和应用价值,是目前国际上热门的前沿研究领域之一。SnO2材料是具有直接带隙的透明氧化物半导体材料,室温下带隙宽度为3.6eV,激子束缚能为130meV。与第三代半导体材料代表GaN和ZnO相比,SnO2具有更宽的带隙和更高的激子束缚能,是一种非常有前途的透明和紫外光电器件材料。长期以来,人们对SnO2的研究主要围绕着透明导电膜和化学气敏传感器等领域的应用,但是,近年来,制备高结晶质量SnO2材料,研究其结构和光电性质的研究越来越多,以期在透明和紫外光电器件领域有更广泛的应用。传统的制备方法(如溅射、热解等)所制备的SnO2薄膜缺陷较多,因而限制了其在半导体器件领域的应用,所以近年来人们制备研究高质量SnO2材料多采用外延生长方法(如PLD、ALD和CVD等)。在这样的背景下,本论文采用金属有机化学气相沉积方法适合制备结构完整的SnO2外延薄膜,且具有可商业化生产的特点,具有一定的科学意义和良好的应用前景。本论文主要分为两大部分：第一部分采用MOCVD方法在TiO2(001)和MgO(100)衬底上制备出了SnO2外延薄膜,并对所制备薄膜的结构及光电性质进行了研究；第二部分制备了Sb掺杂的SnO2外延薄膜,系统的研究了薄膜的结构、光学和电学性质。第一部分的主要工作和结果如下：实验采用MOCVD方法,以高纯Sn(C2H5)4(纯度为6N)为MO源,高纯O2(5N)为反应氧源,超高纯度的N2(9N)为设备载气,分别在TiO2(001)和MgO(100)衬底上制备了不同衬底温度下生长的SnO2薄膜系列,对制备薄膜的结构和光电性质进行了系统研究。1.分别在衬底温度为500℃、600℃和700℃下,在TiO2(001)衬底上制备了SnO2薄膜。结构分析结果表明,不同衬底温度下制备的薄膜均为四方金红石结构的SnO2薄膜,且具有[001]方向的单一取向。通过对薄膜内部结构的分析,确定薄膜的面外外延关系为SnO2(002)//TiO2(002)；面内外延关系为SnO2[010]//TiO2[010]和SnO2[100]//TiO2[100].光学特性测试结果表明,不同衬底温度下制备的样品在可见光区的平均透过率为68%,均超过了衬底本身的透过率66%,具有增透效应。600℃衬底温度下制备的样品在室温下的光致发光谱测量,在615nm附近发现一条比较宽的发光带,经分析为氧空位和缺陷能级引起的。2.分别在衬底温度为500℃、550℃、600℃和700℃下,在MgO(100)衬底上制备出了SnO2薄膜,XRD和HRTEM结果分析表明,所制备薄膜均为四方金红石结构的Sn02薄膜,且具有[110]方向的单一取向。对薄膜的内部结构进行分析,提出了在MgO(100)衬底上制备Sn02(110)薄膜的外延关系原理图,薄膜生长内部具有两重畴结构,并且与MgO[100]是偏转45°角,沿MgO[110]方向生长的,薄膜与衬底的面外外延关系为SnO2(110)//MgO(100),面内外延关系为SnO2[110]//MgO[011],SnO2[001]//MgO[011].薄膜电学性质测量结果表明,600℃衬底温度下制备的薄膜的迁移率最大为17.1cm2.v-1.s-1,载流子浓度最小为2.9×1018cm-3,相应的电阻率为0.126ΩΩ-cm。光学测试分析表明,600℃衬底温度下制备的薄膜样品在可见光区(380nm-780nm)的平均透过率超过了77%,薄膜的光学带隙为3.93eV。第二部分的主要工作和结果如下：实验采用MOCVD方法,以高纯Sn(C2H5)4(6N)和高纯Sb(CH3)3(6N)为MO源,高纯O2(5N)为反应氧源,超高纯度的N2(9N)为设备载气,分别在TiO2(001)和MgO(100).衬底上制备了不同Sb掺杂比例的的SnO2:Sb薄膜系列,对不同掺杂比例对薄膜的结构和光电性质的影响进行了系统研究。1.在600℃的衬底温度下在TiO2(001)衬底上制备了不同Sb掺杂比例(1%、3%、5%和7%)的SnO2:Sb薄膜。XRD和SEM分析结果表明,制备的薄膜均为四方金红石结构的SnO2薄膜,且具有[001]方向的单一取向,除了SnO2(001)面衍射峰外,并未出现8b2O3和Sb2O5的衍射峰,说明Sb元素的掺杂,并未改变薄膜的结构。随着Sb掺杂比例的增加至7%,薄膜结构转变为非晶或多晶结构。光学透过谱显示,SnO2:Sb样品在可见光区的透过率仍然高于衬底TiO2的透过率,具有增透效应。SnO2薄膜的电学性质随Sb掺杂浓度的变化关系为：随着Sb掺杂浓度由0%增加至7%时,霍尔迁移率由18.1cm2.v-1.s-1单调递减至3.4cm2.v-1.s-。随着Sb掺杂浓度由0增至3%,载流子浓度由2.6×1019cm-3增大至4.1×1020cm-3,而当Sb浓度继续增加至7%时,载流子浓度缓慢减小至2.2×1020cm-3。与此相反,随着Sb掺杂浓度的增加,薄膜的电阻率先快速减小,后缓慢增加。薄膜样品的电学性质变化主要与薄膜的电离杂质散射和晶格散射有关。Sb掺杂浓度为3%的薄膜样品具有最佳的电学性能,室温下其电阻率、载流子浓度和霍尔迁移率分别为2.3×10-3Ω·cm、4.1×1020cm-3和6.9cm2.v-1.s-。2.在600℃的衬底温度下在MgO(100)衬底上制备了不同Sb掺杂比例(1%、3%、5%、7%和10%)的SnO2:Sb薄膜。XRD测试结果表明,薄膜都只具有Sn02[110]方向的单一取向。光学透过谱显示,不同Sb掺杂浓度样品的透过率均超过了77%,当Sb掺杂浓度由1%增加至7%时,薄膜带隙由3.98eV增加至4.13eV,当Sb掺杂浓度继续增大至10%时,带隙降为4.10eV,这种变化趋势可以根据Burstein-Moss移动来解释。随着Sb浓度的增加,样品的载流子浓度有所增加,所以带隙变宽。Sn02薄膜的电学性质随Sb掺杂浓度的变化关系为：随着Sb掺杂浓度由0%增加至10%时,霍尔迁移率由17.1cm2·v-1·s-1单调递减至6.3cm2.v-1.s-。随着Sb掺杂浓度由0增至3%,载流子浓度由2.9×1018cm-3增大至5.4×1020cm-3,而当Sb浓度继续增加至7%时,载流子浓度缓慢减小至5.1×1020cm-3。与此相反,随着Sb掺杂浓度的增加,薄膜的电阻率先快速减小,后略有增加。Sb掺杂浓度为3%的薄膜样品具有最佳的电学性能,室温下其电阻率、载流子浓度和霍尔迁移率分别为1.2×10-3Ω.cm、5.4×1020cm-3和9.9cm2.v-1·s-。更多还原

【Abstract】 With the development of the third semiconductors, there has been increasing interest in the research of wide band gap oxide semiconductor. It is a very potential material for transparent and ultraviolet optoelectronic devices, so the study of the wide band gap oxide semiconductor is enormously significant. Nowadays, the field has already been the international front of the research. Tin oxide is a wide band gap semiconductor with direct band gap. Compared with GaN and ZnO, SnO2has a wider band gap3.6eV at room temperature, and a higher exciton binding energy of130meV. In the past, the investigation of SnO2films was mainly focused on the fields of transparent conducting oxides and gas sensors. In resent years, however, there is more attention being paid to the preparation of high quality SnO2films, and the structure and photoelectric properties have been investigated in detail. The SnO2films prepared by the common methods such as sputtering and spray pyrolysis are defective, which is difficult to be used in the field of semiconductor device. Recently, several fabrication methods have been explored to grow the epitaxial SnO2thin films, which include pulsed laser deposition (PLD), atomic layer deposition (ALD) and chemical vapor deposition (CVD). Under such background, epitaxial SnO2thin films are prepared by MOCVD, which is suitable for commercial production. The structure and photoelectric properties of tin oxide films is investigated in detail. The study has both science meaning and practical application foreground.The content of this article contains two parts. In the first part, epitaxial SnO2films were prepared on TiO2(001) and MgO (100) substrate by MOCVD, and the structural and photoelectric properties of the films were investigated. In the second part, SnO2films doped with Sb were prepared on TiO2(001) and MgO (100) substrate by MOCVD, and the structural, optical and electrical properties of the films were studied systematically.The major research work and results of the first part are as follows:SnO2films were prepared on TiO2(001) and MgO (100) at different substrate temperatures by MOCVD. During the deposition processes, high purity Sn(C2H5)4(6N) was used as the MO source, high purity O2was used as the oxidant, ultra high purity N2was used as the carry gas. The structural, optical and electrical properties of the films were investigated.1. SnO2films were deposited on TiO2(001) substrate at different temperatures of500℃,600℃and700℃. Structural analyses showed that the films deposited at different temperatures were rutile structure SnO2with a single orientation of [001] direction. The epitaxial relationship between film and substrate was SnO2(002)//TiO2(002) with SnO2[010]//TiO2[010] and SnO2[100]//TiO2[100]. The optical transmittance spectra showed that the average transmittance in the visible range for all prepared films was over68%, exceeded the transmittance66%for the substrate. The photoluminescence (PL) spectrum of SnO2film deposited at600℃showed a broad band centered at615nm, and the luminescence mechanism could be attribute to the structural defects formed during the growth.2. SnO2films were deposited on MgO (100) substrate at different temperatures of500℃,550℃,600℃and700℃. XRD and HRTEM results showed that the films deposited at different temperatures were rutile structure SnO2with a single orientation of [110] direction. The schematic diagrams of the epitaxial relationships were given. Two domains were formed inside the epitaxial film deposited on MgO (100) substrate. The epitaxial relationship between the film and substrate was SnO2(110)//MgO(100) with SnO2[110]//MgO [011], SnO2[001]//MgO [011]. The Hall mobility of the film prepared at600℃was17.1cm2·v-1·s-1. The carrier concentration of the film was2.9×1018cm-3. And the resistivity of the film was0.126Q-cm. The average transmittance of the sample prepared at600℃in the visible wavelength region (380nm-780nm) exceeded77%, and the optical band gap was3.93eV.The major research work and results of the second part are as follows:SnO2:Sb films were prepared on TiO2(001) and MgO (100) at different substrate temperatures by MOCVD. During the deposition processes, high purity Sn(C2H5)4(6N) and Sb(CH3)3(6N) were used as the MO source, high purity O2was used as the oxidant, ultra high purity N2was used as the carry gas. The structural, optical and electrical properties of the films were investigated systematically.1. SnO2:Sb films were deposited a t600℃on TiO2(001) substrate with various amounts of Sb-doping (1%,3%,5%and7%). The XRD and HRTEM results indicated that the prepared samples were rutile structure SnO2with a single orientation of [001] direction. The phases of Sb2O3and Sb2O5were not been found. With the increase of antimony content, the films changed from epitaxial films to amorphous or microcrystalline. The average transmittance of all the samples in the visible wavelength region (380nm-780nm) exceeded the average transmittance of the substrate. The electrical properties of the films were investigated. As the antimony content increased from0to7%, the Hall mobility of the films decreased from18.1cm2·v-1·s-1to3.4cm2·v-1·s-1. The carrier concentration of the films increased fleetly, and then decreased slowly. On the contrary, the resistivity of the films decreased fleetly, and then increased slowly. The3%Sb-doped SnO2film exhibited the best electrical properties. The resistivity, carrier concentration and Hall mobility for the3%Sb-doped SnO2film were2.3×10-3Ω·cm,4.1×1020cm-3and6.9cm2·v-1·s-1, respectively.2. SnO2:Sb films were deposited a t600℃on MgO (100) substrate with various amounts of Sb-doping (1%,3%,5%,7%and10%). The XRD results indicated that the films were rutile structure SnO2with a single orientation of [110] direction. The average transmittance of all the samples in the visible wavelength region (380nm-780nm) exceeded77%. With the increase of antimony content, the optical gaps of the SnO2:Sb films were in the range of3.98eV-4.13eV. The electrical properties of the films were investigated. As the antimony content increased from0to10%, the Hall mobility of the films decreased from17.1cm2·v-1·s-1to6.3cm2·v-1·s-1. The carrier concentration of the films increased fleetly, and then decreased slowly. On the contrary, the resistivity of the films decreased fleetly, and then increased slowly. The3%Sb-doped SnO2film exhibited the best electrical properties. The resistivity, carrier concentration and Hall mobility for the3%Sb-doped SnO2film were1.2×10-3Ω·cm,5.4×1020cm-3and9.9cm2·v-1·s-1, respectively.更多还原