【作者】 裴选；

【导师】 计峰；

【作者基本信息】 山东大学 ， 微电子学与固体电子学， 2010， 硕士

【摘要】 透明导电氧化物(TCOs)薄膜由于其宽带隙、高电导率、可见光范围内极高的透过率以及红外波段高的反射率等特性,被广泛应用于各种光电器件,如太阳能电池、热镜、表面声波器件和液晶显示器的透明导电电极等。由于本征施主型缺陷的存在,如间隙金属原子、氧空位以及反位原子等,未人为掺杂的TCO大多为n型半导体。众所周知,pn结是大部分半导体器件的核心部件,p型TCO的缺失大大制约了透明导电氧化物的应用,因此p型TCO的制备成为了当今半导体方面研究的热点。如果能开发出p型导电的TCO,将会在白光LED、紫外LED、CMOS低功耗电路等小型高性能元器件和大面积LED、透明太阳能电池、红外线反射玻璃等大面积元器件上取得突破性进展。氧化锡(SnO2)是一种直接带隙宽禁带半导体材料,跟其他材料相比,具有禁带宽度大、激子束缚能高,常温下分别为3.6-4.0 eV和130 m eV(ZnO分别为-3.3 eV和60 m eV)、制备温度低、化学稳定性好等显著优点,有关SnO2基薄膜的制备及性能的研究,已成为透明导电薄膜材料和传感器材料等研究领域中一个很重要的部分,在近几年得到了迅猛的发展。三价材料的掺杂在理论上可以实现SnO2导电类型的转换。目前,采用金属有机化学气相沉积(MOCVD)方法制备掺镓氧化锡和镓氮共掺氧化锡薄膜的研究尚未见诸报道。本文中,我们使用MOCVD方法制备了Ⅲ族镓元素单一掺杂以及Ⅲ族和Ⅴ族元素(镓氮)共掺的SnO2薄膜,并详细研究了掺杂对薄膜结构以及光电性质的影响。本论文的研究工作及结果如下：1.采用MOCVD方法,以高纯(C2H5)4Sn为锡源,(CH3)3Ga为镓源,高纯O2为氧化剂,高纯N2为载气,在400-600℃的蓝宝石(0001)衬底上制备了同一浓度掺杂的SnO2：Ga薄膜。X射线衍射(XRD)测试结果显示,在500℃条件下生长薄膜最易得到单晶结构。随后,在500℃生长温度下,制备了一系列掺杂浓度不同的SnO2：Ga薄膜,掺杂浓度从3%到15%。对制备的样品的结构、光学和电学性质进行了研究。XRD测试结果表明,制备的所有薄膜均为SnO2四方金红石结构,且具有沿a轴的高度择优取向性。在200-900 nm波长范围内测试了样品的光学透射谱,薄膜透过率均大于85%。根据(ahv)2-hv曲线可以得出其光学带隙Eg,且Eg随掺杂浓度的不同而发生变化。对掺杂3%和15%的薄膜,详细研究了其光致发光PL谱,得出了Ga处于间隙位置充当施主和取代Sn格点充当受主时的能级位置,分别位于导带底下0.12 eV和价带顶上0.25 eV处。掺杂会对薄膜的结构及结晶质量产生影响,从而导致其电学性质随掺杂浓度发生变化。同时我们还研究了空气中不同温度退火对薄膜性质造成的影响。2.采用MOCVD方法,在500℃的蓝宝石(0001)衬底上制备了镓氮共掺的SnO2薄膜。同上,以高纯(C2H5)4Sn为锡源,(CH3)3Ga为镓源,高纯O2为氧化剂,高纯N2为载气,氮由高纯NH3来提供。对制得的样品在氮气中进行不同温度的退火。对样品进行了XRD、扫描电子显微镜(SEM)、霍尔效应和透过率测试,详细研究了掺杂对薄膜的结构形貌特征、电学性质和光学性质的影响。另外,通过比较镓氮共掺氧化锡薄膜和掺镓氧化锡薄膜的性质,探讨了氮的掺入对薄膜的影响。更多还原

【Abstract】 Transparent conducting oxides (TCOs) films are widely used in many photoelectric d eVices, such as solar cells, heat mirrors, surface acoustic wave d eVices and liquid-crystal as transparency electrodes, which is due to their wide band gaps, high conductivity and high transmittance in the visible region and high reflectivity in infrared region. Most of the unintentional doped TCOs films are n-type semiconductors due to the intrinsic defects, such as interstitial atoms, oxygen vacancies and anti-position atoms, which restrains their application badly. If p-type TCOs can be fabricated, there will be a breakthrough in the small-scale high performance components, such as white LED, ultraviolent LED and circuits with low power, and in the large-scale components, such as large-scale LED, transparent solar cells and reflective infrared glasses and so on.SnO2 is a wide direct band gap semiconductor material and compared with other materials, it has many advantages such as a wider band gap of 3.6-4.0 eV, higher exciton binding energy of 130 m eV (-3.3 eV and 60m eV for ZnO, respectively), lower growth temperature and higher chemical stability. As an important part of the research of transparent conducting and sensor materials, the fabrication and properties investigation of SnO2 and doped SnO2 films have made a rapid progress in recent years. In theory, the conduction type can be changed by IIIA element doping. Until now, few reports have been published on the properties of gallium doped films and gallium and nitrogen co-doped SnO2 films prepared by MOCVD. In this paper, SnO2:Ga and SnO2:Ga-N films were fabricated by MOCVD, and the effect of doping on the structural and opto-electrical properties of the films are being investigated in detail.The major work and results are as follows:1. SnO2:Ga films with various concentration of gallium were fabricated on sapphire (0001) using a MOCVD system. High purity tetraethyl tin (C2H5)4Sn was employed as Sn organometallic (OM) source, trimethyl gallium (CH3)3Ga as Ga OM source, O2 as oxidant and N2 as carrier gas. The structural, optical and electrical properties of samples were investigated in detail. The XRD spectra show that all films have the rutile structures of SnO2 and have a high degree preferred orientation along a-axis. Measurement of transmittances has been taken in the wavelength range of 200-900 nm. The optical band gaps of films can be obtained according to the (ahv)2～hv plots, and they varied with the content of dopant. The PL spectra of 3% and 15% doped SnO2:Ga films were discussed in detail. The energy 1 eVel of interstitial Ga acting as donor is 0.12 eV below the bottom of conduction band, and 0.25 eV above the valence band maximum for the substitutional Ga for Sn serving as acceptor. The electrical properties of the samples varied with the doping. Also, the effects of annealing on the properties of films were investigated in the paper.2. Ga and N co-doped SnO2 films were deposited onα-Al2O3 by MOCVD. Sn and Ga OM sources were the same as above. NH3 was used as N resource. The as-deposited films were annealed for 2 h in nitrogen at different temperatures. XRD, SEM and transmittance were performed, and structural and optical properties were discussed. In addition, by comparing the properties of Ga and N co-doped films with Ga doped films, the effect of N on the properties of the films were investigated.更多还原