【作者】 么艳平；

【导师】 薄报学；

【作者基本信息】 长春理工大学 ， 光学工程， 2009， 博士

【摘要】 Ⅲ-Ⅴ族晶体半导体材料由于其稳定性好,高吸收系数、高迁移率,可望在室温工作等特点已引起人们广泛注意。与晶体Ⅲ-Ⅴ族半导体相比,非晶态半导体材料具有成本低、制备工艺简单的优点。Ⅲ-Ⅴ族非晶半导体仍具有半导体特性,有望应用于探测器（适用波段1～3μm）以及其它光电器件。但是目前国内外还缺乏Ⅲ-Ⅴ族非晶态材料全面和详尽的研究。本文围绕非晶（a-）In_xGa_1-xAs（0≤x≤1）薄膜和a-InSb薄膜的制备、表征、退火和氢钝化四个方面开展工作。（一）Ⅲ-Ⅴ族非晶薄膜的制备工艺在玻璃和单晶硅衬底上,我们利用磁控溅射方法制备了Ⅲ-Ⅴ族非晶薄膜。通过材料的生长机理和动力学研究,分析了工艺参数对结构的影响。减小功率、降低衬底温度或增加工作气压可以减小溅射粒子的能量,制备出非晶薄膜。通过大量的实验,我们确定了a-In_xGa（1-x）As薄膜和a-InSb薄膜的生长窗口。1、a-GaAs薄膜制备工艺条件:在室温条件下,溅射功率(P_rf)为40-100W,工作气压（P_w）为0.5-8 Pa。2、对于制备a-InAs薄膜,在P_rf一定时,不同的衬底温度T_S存在不同的门槛气压使制备样品结构从多晶态向非晶态转变,并且随T_S增加,门槛气压也随之增加。3、通过调整InAs靶和GaAs靶的功率,可以制备出a-InGaAs薄膜。4、在室温条件下,P_rf为50W,P_w为3Pa以上时,制备InSb薄膜为非晶结构。（二）Ⅲ-Ⅴ族非晶薄膜的结构、组分、形貌和光电性质表征采用X射线衍射仪、透射电镜、X射线能谱仪、原子力显微镜、扫描电镜等手段对Ⅲ-Ⅴ族非晶薄膜的结构、组分和表面特性进行了表征,分析了工艺参数对结构、组分和形貌的影响,我们已获得了表面形貌很好、符合化学计量比的a-In_xGa（1-x）s和a-InSb薄膜。并且由X射线衍射结果计算出径向分布函数和双体相关函数,获得了a-In_xGa_1-xAs薄膜的微观结构数据。a-GaAs和a-InAs薄膜的最近邻原子的配位数小于4,说明含有一定的错键。a-InGaAs薄膜的径向分布函数第一近邻峰分裂成位于2.58（?）和2.7（?）的两个峰,分别对应Ga-As键和In-As键的键长,并且随In成分的增加,位于2.58（?）处的峰的相对峰高变小,而2.7（?）处的峰的相对峰高变大。我们利用分光光度计和椭圆偏振光谱仪分析了a-In_xGa（1-x）As和a-InSb薄膜的光学性质。工艺参数直接影响光学带隙的变化,随P_w的增加或P_rf减小,导带带尾和价带带尾的缺陷态减小,光学带隙相应增加。实现a-In_xGa（1-x）As薄膜的光学带隙变化范围为0.72eV-1.77 eV;a-InSb的光学带隙在0.462-0.61eV之间。实验中发现,在一定条件下制备InGaAs薄膜的光学带隙与In含量的关系不确定。通过椭圆偏振光谱获得了薄膜光学常数,发现非晶、多晶和单晶薄膜的椭圆偏振光谱表现出巨大的差异。采用Hall系统进行了非晶薄膜的电学特性分析,薄膜的无序化程度越高,电阻率越大、载流子浓度越小。对a-In_xGa（1-x）As薄膜和a-InSb薄膜的光敏特性进行了分析。实验制备的a-InGaAs、a-InSb薄膜在光照下具有明显的光敏特性。在a-GaAs和a-InSb薄膜中,光敏随气压的增加而增加。然而对于a-In.As薄膜,符合化学计量比时光敏最大,但是要比a-GaAs、a-InGaAs和a-InSb薄膜光敏小。（三）Ⅲ-Ⅴ族非晶薄膜的退火研究对a-In_xGa_1-xAs薄膜进行了退火实验,晶化温度约为300℃。在晶化温度以下退火,可以减少带尾中的缺陷以及增加应变键的驰豫,由此导致光学带隙增加。随退火温度增加而出现结晶相,光学带隙减小。并且由于多晶相和非晶相的交界面上,形变键和悬挂键数目增加,带尾宽度增加。对a-GaAs:H薄膜进行了退火实验,发生氢的释放,光敏下降。（四）a-In_xGa_1-xAs薄膜的掺氢研究实现发现,溅射过程中加H₂对a-In_xGa_1-xAs薄膜有钝化作用,减少了带尾和带隙中的态密度,导致吸收边蓝移、光电导增强。同时发现,加H₂易于造成a-InAs薄膜的晶化。总之,我们采用磁控溅射技术制备Ⅲ-Ⅴ族非晶薄膜,并且研究了工艺参数对结构、组分、表面形貌和光电性能的影响。通过优化工艺参数,我们可以制备出具有光电响应,能应用于光导探测器的Ⅲ-Ⅴ族非晶薄膜,这为Ⅲ-Ⅴ族非晶薄膜的将来应用提供了实验依据。更多还原

【Abstract】 Ⅲ-Ⅴcrystalline materials have attracted widespread attention because of its better thermal stability,higher absorption coefficient,higher carrier mobility and possibility of application at room temperature.Compared withⅢ-Ⅴcrystalline semiconductors, amorphous semiconductors have some attractive characters such as low cost and easy preparation process.MoreoverⅢ-Ⅴamorphous materials keep semiconductor properties, led to their potential applications in future detectors（application band:1～3μm） and other optoelectronic devices.But amorphousⅢ-Ⅴsemiconductors are still lack of systematic and detailed study.In this paper,our study on amorphous（a-） In_xGa_1-xAs and a-InSb films includes the preparation,characterization,annealing and hydrogen passivation.Main contents are as follows:1.The preparation process of amorphousⅢ-ⅤfilmsAmorphousⅢ-Ⅴfilms are deposited on substrates of glass and silicon by RF magnetron sputtering technique.Based on the studies of material growth mechanism and kinetics analysis,we analyze the effects of sputtering parameters on the structure of film.In order to prepare amorphous films,we must reduce the energy of sputtering particle by means of decreasing sputtering power P_rf,lowering substrate temperature T_S or increasing working pressure P_w.Through many experiments,we have obtained“growth window”used for a-In_xGa_1-xAs and a-InSb films.The conclusions are summarized as follows:（1）When P_w is in the range of 0.5-8 Pa,we obtain a-GaAs film with T_S of 20℃and P_rf of 40-100 W.（2）For each value of T_S,the results of InAs films show the existence of a threshold value of P_w.The films are amorphous above threshold value and the films are polycrystal below threshold value.This threshold value of P_w also increases with increasing P_rf.（3）We have deposited a-In_xGa_1-xAs films by changing RF power of GaAs target and RF power of InAs target.（4） At T_S=20℃,we obtain a-InSb films when P_rf is 50W and P_w is higher than 3 Pa.2.The characterization of amorphousⅢ-ⅤfilmsWe have characterized structure,surface morphology and composition of amorphous films by means of X-ray diffractometer（XRD）,transmission electron microscopy（TEM）, scanning electron microscopy（SEM） and electron diffraction spectroscopy（EDS）.Through the systematical study the effect of sputtering parameter on the structure、surface morphology and composition,we have prepare stoichiometric amorphous films with better surface morphology.And we calculate the radical distribution function and pair correlation function from XRD in order to obtain microstructure data of a-In_xGa_1-xAs thin films.For a-GaAs and a-InAs films,coordination numbers of the first neighbouring atoms is smaller than 4 due to the presence of wrong bonds in films.The radical distribution function of a-InGaAs separates two peaks at 2.58（?） and 2.7（?）,respectively.We assign them to Ga-As band and In-As band.With the content of In increasing,the intensity of the peak at 2.5 8（?） decrases and the peak at 2.7（?） changes reversely.We characterize the optical properties of a-In_xGa_1-xAs and a-InSb thin films by spectrophotometer and the ellipsometry.We have investigated how process parameters influence the optical band gap of amorphous semiconductors.Experimentally,it is found that optical band gap broadens with increasing P_w or decreasing P_rf because the breadth of band tail reduces.The optical band gap of a-In_xGa_1-xAs films shifts from 0.72eV to 1.77 eV.And optical gap of a-InSb is in the range of 0.462-0.61eV.But we don’t find the definite relation between optical band gap and In content for a-In_xGa_1-xAs films.We obtain optical constants of thin films from ellipsometry.The optical constants of amorphous films show enormous differences from polycrystal films and monocrystal films.We study the electrical properties of thin films using Hall system.The results suggest greater levels of disorder leads to smaller carrier concentration and larger resistivity. a-In_xGa_1-xAs and a-InSb thin films have obvious photosensitive properties at light.The photo sensitivity increases with increasing working pressure for the case of a-GaAs.We have found the similar trend in a-InSb.But the photo sensitivity is only obvious in the stoichiometric a-InAs film.Compared with photo sensitivity in a-GaAs and A-InSb,the value in a-InAs is smaller.3.The study on annealing of amorphous a-In_xGa_1-xAs filmsWe have carried out annealing experiments.The experiment results show crystallization temperature of a-In_xGa_1-xAs films is about 300℃.We have observed the optical gap shifts to higher energies as annealing temperature is below crystallization temperature.We propose that these changes are due to a diminution of the tail state defects and/or the relaxation of strained bonds.When annealing temperature is higher than crystallization temperature,the optical gap decreases.And the the breadth of band tail increases due to an increase of the number of distorted and broken bonds in the interface between the crystalline clusters and the amorphous matrix.Moreover we have found H releases from a-In_xGa_1-xAs films and photo sensitivity decreases while annealing.4.The study on amorphousⅢ-Ⅴfilms doping hydrogenWe investigate the passivation of hydrogen on the amorphousⅢ-Ⅴfilms.Hydrogen induces blue shifts in absorption edge and increasing of photoconductivity.We also have found doped hydrogen results in crystallization for a-InAs films. In summary,we have depositedⅢ-Ⅴamorphous films by RF magnetron sputtering. Moreover we have investigated the effects of sputtering parameters on the structure,surface morphology,composition and properties.We can obtainⅢ-Ⅴamorphous films for detector through optimizing deposited conditions.Our study provides practical experience for their potential applications in future detectors.更多还原