二维层状晶体场效应器件电学性质的温度效应研究

发布时间：2018-01-15 17:19

本文关键词：二维层状晶体场效应器件电学性质的温度效应研究　出处：《电子科技大学》2016年博士论文　论文类型：学位论文

【摘要】：近年来,受制于传统硅材料的物理极限,硅基微电子器件要继续遵循摩尔定律进行发展面临着极大的困难。二维层状材料,包括石墨烯和金属硫属化合物,因其具有优异的电子迁移率、独特的光电性能、原子级厚度等特点,被视作可替代传统硅材料的下一代微电子器件材料。而对硅基微电子器件的研究表明,器件在工作中由于热量积累造成的器件温度升高会导致器件一系列的性能变化。硅基微电子器件中的热效应已经对器件进一步发展产生了限制。因而在目前二维层状材料还处于应用研究初期的阶段,及早地对利用二维层状材料所形成的微电子器件性能与器件温度变化的关系进行研究,无疑有助于未来这一类新兴电子器件的实际应用和推广。而在种类繁多的微电子器件中,场效应器件是一种基础性器件。因此,针对二维层状材料,选取场效应器件作为研究对象来对微电子器件的温度效应进行研究,是非常必要的。针对这一问题,本论文分别对两种典型的二维层状材料场效应器件,石墨烯场效应器件和金属硫属化合物SnS_(2-x)Se_x场效应器件的温度效应,有重点地展开了一些研究工作。通过对石墨烯场效应器件温度效应的研究,发现了石墨烯场效应器件在长时间工作时自发热引起的沟道电阻不稳定性,分析了这种不稳定性的成因。在成功实现了高导热AlN介电层薄膜制备的基础上,通过用其作为器件的介电层,有效的抑制了沟道中热量的积累,减弱了沟道电阻不稳定性。利用化学气相输运法合成了不同化学组分比的SnS_(2-x)Se_x层状晶体,对相应的场效应器件在不同温度下的转移特性和输出特性进行了系统的表征和分析。通过对输运特性的分析和相关理论计算,解释了S/Se比例对晶体在不同温度下输运特性和晶体激活能影响。在石墨烯场效应器件的温度效应问题上,首先对Si(001)上高导热AlN薄膜的射频反应溅射制备工艺进行了研究。通过对溅射功率的优化控制,观察到通过适当调高溅射功率,可以有利于高能Al-N键的形成,从而得到c轴择优取向的AlN薄膜。结合考虑氧杂质和晶界的散射模型及薄膜热导率测试数据,分析了反应溅射气氛中Ar/N2流量比对薄膜热导率的影响,得到了优化的反应溅射气氛。通过对不同衬底温度下生长的Al N薄膜热导率以及AlN与Si衬底界面微结构的表征,结合串联热阻模型和散射模型解释了衬底加热温度-界面微结构-热导率三者之间的相互关系。通过提高衬底加热温度,抑制AlN/Si界面处非晶AlN层的形成,成功制备了热导率可达26.7 W/mK的高导热介电层薄膜。在实现了高导热AlN介电层薄膜制备的基础上,对石墨烯场效应器件在80 K至300 K温度区间内存在大气环境杂质时的自发热效应表现进行了测试和分析。发现当石墨烯场效应器件在0.5 W功率下工作500 s过程中,器件的沟道电阻在器件处于p型导电态和n型导电态时会分别呈现工作时逐渐上升和下降的变化。通过对器件工作前后电中性点电压的测量以及输运机理的讨论,得出这一沟道电阻不稳定性的来源是石墨烯场效应器件由于自发热效应造成沟道中p型杂质解吸附,进而使石墨烯上载流子的浓度产生了变化。通过比较SiO2薄膜和AlN薄膜分别作为介电层的石墨烯场效应器件在80 K至300 K温度区间下不同的沟道电阻变化规律及两种薄膜的热物性,表明通过将介电层替换为高导热AlN介电薄膜可以有效地抑制沟道电阻在长时间工作时的不稳定变化。在对金属硫属化合物SnS_(2-x)Se_x场效应器件的研究中,利用化学气相输运法制备了不同Se含量的SnS_(2-x)Se_x层状晶体,并对相应的场效应器件在90 K至295 K温度区间下的转移特性和输出特性进行了表征。发现在90 K至295 K的整个温度区间,随着Se含量的升高,在x≥1.2时,器件在栅压为-50 V至50 V范围内基本无法实现“关断”。沟道中晶体与器件金属电极之间的接触类型也会随着Se含量的升高发生由近似欧姆接触向肖特基接触的转变。从能带结构变化的角度出发,对Se含量变化与器件在不同温度下性能变化的关系进行了解释,表明Se含量的增加实际上属于一种n型掺杂。基于所测得的器件沟道电阻与温度的关系,从实验和理论计算两方面分析了Se含量对晶体激活能大小的影响,表明利用类氢模型能够较为准确的描述Se含量变化对能带结构的影响。而这种能带结构的变化本质上是Se含量不同所造成的晶体介电常数改变主导的晶体激活能变化。
[Abstract]:In recent years, subject to the physical limit of traditional silicon material, silicon microelectronic devices will continue to follow Moore's law of development is facing great difficulties. Two dimensional layered materials, including graphene and metal chalcogenides, due to its excellent optical electron mobility, unique electrical properties, atomic thickness etc., are as an alternative to traditional silicon materials for the next generation of microelectronic devices and materials. Study of silicon-based microelectronic devices show that the device at work due to heat accumulation caused by the device temperature will lead to changes in performance of a series of devices. The thermal effect of Si based microelectronic devices have on the further development of the device in limit. The two-dimensional layered materials is still in the early stage of applied research, relationship between microelectronic device properties and device temperature changes early on the use of two-dimensional layered materials formed by the The research, undoubtedly contribute to the application and promotion of the future of this kind of emerging electronic devices. In a wide variety of microelectronic devices, field effect devices is a basic device. Therefore, the two-dimensional layered materials, selection of field effect devices as the temperature effect on the microelectronics research subject, is very necessary. To solve this problem, in the paper, two typical two-dimensional layered material field effect devices, graphene field-effect devices and metal chalcogenide SnS_ (2-x) temperature effect of Se_x field effect devices, mainly carried out some research work. Through the research on graphene field effect devices temperature effect the discovery channel resistance of graphene field-effect devices for a long time. Since the heat induced instability, analyzes the causes of this instability. After the successful implementation of the high thermal conductivity of AlN thin dielectric layer On the basis of membrane preparation, by using it as the dielectric layer of the device, can effectively restrain the heat accumulation in the channel, weakened the channel resistance instability. Using chemical vapor transport method for the synthesis of different chemical composition than the SnS_ (2-x) Se_x layered crystal, the transfer characteristics and output the characteristics of the corresponding field effect devices at different temperatures were characterized and analyzed by the system. The transport characteristics analysis and theoretical calculation, explain the effect of S/Se ratio on crystal at different temperature transport properties and crystal activation energy. The temperature effect in graphene field effect devices, first of all Si (001) process of RF Reactive Sputtering on the high thermal conductivity of AlN thin films were studied. The control through optimization of the sputtering power, observed by appropriate high sputtering power, can be conducive to the formation of Al-N bond energy, so as to get the c axis preferred orientation The AlN thin film. Considering the scattering model and the thin film thermal conductivity and oxygen impurity grain rate test data, analyzes the influence of Ar/N2 flow ratio on the thermal conductivity of thin films by reactive sputtering atmosphere, were obtained. The optimized sputtering atmosphere at different substrate temperatures and growth of Al N thin film thermal conductivity and AlN interface with the Si substrate structural characterization, combined with series resistance model and scattering model to explain the relationship between substrate temperature interface micro structure thermal conductivity three. By increasing the substrate temperature, inhibit the formation of AlN/Si at the interface of the amorphous AlN layer, the thermal conductivity is 26.7 W/mK high thermal conductivity and dielectric layer film successful preparation. In the realization of the high thermal conductivity of AlN dielectric thin films prepared on the basis of the self heating effect of graphene field-effect devices exist in atmospheric environment of impurities in the 80 K to 300 K temperature range were measured and divided Analysis. When the graphene field effect devices operating in the 0.5 W power 500 s, the channel resistance device changes were present when working gradually increased and decreased in the device in P type conductive state and N conductive state. The device before and after the measurement of electrical neutral point voltage and transport the mechanism of discussion, that source of this instability is the channel resistance of graphene field-effect devices due to self heating effect caused by the P channel in the solution and the concentration of impurity adsorption of graphene on the carriers have changed. Through the comparison of the SiO2 and AlN films were used as the thermal properties of graphene dielectric layer the field effect device different from 80 K to 300 K temperature range under the channel resistance variation and two kinds of films, that through the dielectric layer with high thermal conductivity AlN dielectric films can effectively suppress the channel resistance in a long time. The variation in SnS_. Compounds of metal sulfide (2-x) on Se_x field effect devices, different content of Se SnS_ transport was prepared by chemical vapor transport (2-x) Se_x layered crystals, and the transfer characteristics and output characteristics of field effect devices corresponding to the 90 K to 295 K temperature range the findings were investigated. In the 90 K to 295 K in the whole temperature range, with the increase of Se content in X was higher than 1.2, the device at the gate voltage of -50 V to 50 V range impossible to "turn off". The type of contact between the crystal and metal electrode device in the channel will with the increasing shift to Schottky contact by an ohmic Se content. Starting from the band structure of the view of the relationship between the changing of performance changes and devices Se content at different temperatures were explained that the increase of Se content in fact is a kind of N type doping. Based on the measured The relationship between the channel resistance and temperature, from experimental and theoretical analysis of two aspects of the content of Se can activate effect on the size of crystal, shows that the model can describe the change of hydrogen content of Se accurately. The influence on the band structure and the changes of the band structure of the material is dielectric crystal the constant Se content caused by the different changes in the dominant crystal activation energy changes.

【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN386

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