氧化镓MSM日盲紫外光电探测器的研制

发布时间：2018-05-24 08:05

本文选题：β-Ga_2O_3 + (In_xGa_(1-x))_2O_3　；参考：《电子科技大学》2017年硕士论文

【摘要】：近年来,关于β-Ga_2O_3日盲紫外探测技术的研究发展迅猛。β-Ga_2O_3的禁带宽度为4.9 eV,具有高的透光率、化学稳定性好、机械强度高等特点,是一种很好的日盲紫外敏感材料。由于金-半-金(Metal-Semiconductor-Metal,简写为MSM)型器件具有制备简单、响应度高以及与CMOS良好的工艺兼容性等优点,故本论文以MSM为器件基本结构,采用分子束外延技术生长了β-Ga_2O_3薄膜,并制备了日盲紫外探测器。论文具体内容如下:论文首先研究了金-半接触特性对器件性能的影响,对比研究了Ti/Au电极与Au电极对器件性能的影响,在未对电极进行退火处理的情况下,与采用Au电极的器件相比,采用Ti/Au电极的器件性能更优,为此,论文选用Ti/Au作为金属电极材料制备氧化镓MSM日盲紫外探测器。在此基础上,为了探索金-半界面特性对器件性能的影响,论文进一步研究了电极的快速退火处理对氧化镓MSM器件性能的影响,并探讨了其影响机制。论文分别在400℃、500℃、600℃、700℃下对Ti/Au电极进行快速退火处理,测试了退火后器件的I-V特性、时间响应特性,并利用二次离子质谱(SIMS)和X射线光电子能谱(XPS)技术分析了界面微观特性。研究结果表明:经快速退火后,Ti原子扩散进入氧化镓表层与O结合生成TiO2,一方面,降低了界面的金-半接触势垒高度,另一方面,也导致界面附近氧化镓薄膜中产生了更高浓度的氧空位,提高界面势垒处的载流子浓度,使器件的光电流和暗电流都随着电极退火温度的升高而增大,从而提高了器件的光响应度。然而,也正是因为界面氧空位浓度的增加,由于氧空位对电子的陷阱效应,导致了器件更加严重的持续光电导效应(persistent photo-conductivity,简写为PPC),器件响应速度变差。在金-半接触特性研究基础上,为了提高器件的光响应度,论文研究了掺In氧化镓薄膜(In_xGa_(1-x))_2O_3的光电性能。为此,论文首先探索了薄膜的掺铟量与In源温度的关系,并利用EDS、AFM、XPS、紫外可见光谱等来表征薄膜的性质。EDS测试结果显示:当基片温度固定为760℃时,In源温度为700℃时,In源含量为11.5%,这说明:可以通过控制In源温度对(In_xGa_(1-x))_2O_3薄膜中的In含量进行有效调控。为了研究不同In源温度所制备(In_xGa_(1-x))_2O_3薄膜的性质,论文研究了其MSM光电导器件的I-V特性、时间响应特性以及紫外光谱响应,测试结果显示:当In源温度低于600℃时,器件性能未发生显著变化,当In源温度为650℃时,器件的性能明显改善,但当In源温度为700℃时,器件综合性能反而变差,暗电流为9.8 mA,光电流为10.3 mA,虽然响应度达到7.1×104 A/W,但光暗电流比仅为1。AFM分析结果显示:当In源温度为700℃时,薄膜表面出现凸起的类似球状物形貌;经XPS分析得知薄膜表面In析出形成In_2O_3相,这表明:(In_xGa_(1-x))_2O_3薄膜存在严重的晶相分离,从而导致器件性能变差。由于In的高挥发性,薄膜中的In含量不仅与In源温度有关,而且受基片温度影响,为了减弱薄膜的晶相分离程度,论文通过大量实验对基片温度和In源温度进行优化,优化的基片温度和In源温度分别为560℃和600℃,利用此条件下生长的(In_xGa_(1-x))_2O_3薄膜所研制MSM探测器综合性能较好,暗电流为424 pA,光电流为1.06μA,光暗电流比为2.5×103,响应度为73.6 A/W,展现出了较好的日盲紫外光电探测的器件性能。
[Abstract]:In recent years, the research on beta -Ga_2O_3 daily blind ultraviolet detection has been developing rapidly. The band gap of beta -Ga_2O_3 is 4.9 eV, with high transmittance, good chemical stability and high mechanical strength. It is a very good daily blind UV sensitive material. Because of the gold half gold (Metal-Semiconductor-Metal, MSM) type device, it has the preparation of simple materials. Single, high responsiveness and good compatibility with CMOS technology, this paper uses MSM as the basic structure, uses molecular beam epitaxy technology to grow beta -Ga_2O_3 thin film, and has prepared a daily blind ultraviolet detector. The contents of this paper are as follows: firstly, the influence of gold and semi contact characteristics on the performance of the device is studied, and Ti/A is compared and studied in this paper. The effect of the U electrode and the Au electrode on the performance of the device is better than that of the devices using the Au electrode in the condition that the electrode is not annealed. Therefore, Ti/Au is used as the metal electrode material to prepare the gallium oxide MSM daily blind ultraviolet detector. On this basis, the gold and semi interfacial properties are explored. The influence of the device performance is further studied, and the influence of the fast annealing treatment on the performance of gallium oxide MSM devices is further studied and its influence mechanism is discussed. The paper deals with the rapid annealing of the Ti/Au electrode at 400, 500, 600 and 700, respectively, and tests the I-V characteristics, the time response characteristic of the annealed device, and the use of two ions. Mass spectrometry (SIMS) and X ray photoelectron spectroscopy (XPS) techniques have been used to analyze the microscopic characteristics of the interface. The results show that after rapid annealing, the diffusion of Ti atoms into the surface of gallium oxide is combined with O to produce TiO2. On the one hand, the gold and semi contact barrier height of the interface is reduced. On the other hand, the higher concentration of gallium oxide thin films near the interface is produced. The oxygen vacancy, increasing the carrier concentration at the barrier at the interface, makes the photocurrent and dark current of the device increase with the increase of the annealing temperature of the electrode, thus improving the optical responsivity of the device. However, it is also because of the increase in the oxygen vacancy concentration of the interface, which causes the device to continue to be more serious due to the trap effect of the oxygen vacancy on the electric device. The photoconductivity effect (persistent photo-conductivity, abbreviated as PPC), the response speed of the device is poor. On the basis of the study of the gold and semi contact characteristics, in order to improve the optical responsivity of the device, the photoelectric properties of the In_xGa_ (In_xGa_ (1-x)) _2O_3 doped with In are studied. EDS, AFM, XPS, and UV visible spectra are used to characterize the properties of the thin films. The results show that when the substrate temperature is fixed at 760 C, the In source temperature is 700, and the In source content is 11.5%. This shows that the In content in the In_xGa_ (1-x) _2O_3 thin film can be effectively controlled by controlling the temperature of the In source. In order to study the temperature of the different In sources. The properties of (In_xGa_ (1-x)) _2O_3 film are prepared. The I-V characteristics, time response characteristics and UV spectral response of the MSM photoconductivity device are studied. The test results show that the performance of the device has not changed significantly when the temperature of the In source is below 600 C. When the temperature of the In source is 650, the performance of the device is obviously improved, but the temperature of the In source is 700. The overall performance of the device becomes worse, the dark current is 9.8 mA and the photocurrent is 10.3 mA. Although the response degree is 7.1 * 104 A/W, the light dark current ratio is only 1.AFM analysis results show that when the In source temperature is 700, the surface of the thin film appears to be similar to the shape of the spheroid, and the XPS analysis shows that the surface of the thin film is formed to form In_2O_3 phase, which indicates: (I N_xGa_ (1-x)) _2O_3 thin film has serious crystalline phase separation, resulting in poor performance of the device. Because of the high volatility of In, the In content in the film is not only related to the temperature of the In source, but also influenced by the temperature of the substrate. In order to weaken the degree of crystal phase separation of the film, the paper optimizes the substrate temperature and the temperature of the In source by a large number of experiments. The film temperature and In source temperature are 560 C and 600 C respectively. The MSM detector developed by the (In_xGa_ (1-x)) _2O_3 film under this condition has better comprehensive performance, the dark current is 424 pA, the photocurrent is 1.06 A, the light dark current ratio is 2.5 x 103, the response degree is 73.6 A/W, showing the better device performance of the daily blind ultraviolet photoelectric detection.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN23

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