块状半导体材料制备过程的理论和实验研究

发布时间：2019-02-17 16:58

【摘要】：本文针对物理气相输运方法(physical vapor transport,PVT)制备Si C单晶以及机械合金化结合等离子体烧结(MA-PAS)的方法制备掺入S元素的Bi2Te3-基热电材料这两个比较典型的大块状半导体材料的制备过程分别进行了数值模拟与实验研究。作为第三代半导体材料的典型代表,Si C由于其优良的理化性质而被广泛运用在高温度、强辐射、高电压、高电流密度的极端条件下的半导体器件中。PVT法是生产大块状Si C单晶最常用的一种方法,因为在PVT生长Si C单晶的过程中,装置是完全封闭的,我们很难实时的检测生长腔内的温度,物质浓度等相关物理量的变化,所以有必要运用数值模拟的方法来对该过程预先做出数值模拟研究以指导实际的生产过程。通过研究我们发现生长腔内轴向上的温度梯度、操作压力、籽晶表面温度等工艺参数对于晶体生长速率具有重要的影响,具体说来,随着生长腔内温度梯度的增加,压力的降低或者是生长温度的升高,Si C的晶体生长速度加快。Bi2Te3系热电材料因其在室温下良好的热电性能而被广泛运用,但是因为中温区的热电材料多含有Pb等重金属元素,在生产与使用相关热电器件的过程中都会对环境产生不利影响,因此我们希望能够拓展Bi2Te3系热电材料的适用温度范围。在用MA-PAS制备Bi2Te3系块状材料并进行后续测量的实验过程中,我们发现通过在Bi2Te3中掺入S元素,可以很好地提高材料在中温区的热电相关的电学性能,其中Bi2Te2.5S0.5表现出很好地可以在中温下运用的潜力。
[Abstract]:In this paper, the physical vapor transport method (physical vapor transport, Preparation of Si C single crystals by PVT and mechanical alloying combined with plasma sintering (MA-PAS) to prepare Bi2Te3- based thermoelectric materials doped with S Numerical simulation and experimental research are carried out. As a typical representative of the third generation semiconductor materials, Si C is widely used in high temperature, strong radiation and high voltage because of its excellent physical and chemical properties. In semiconductor devices with high current density at extreme conditions, PVT method is the most commonly used method to produce large bulk Si C single crystals, because the device is completely closed during the growth of Si C single crystals by PVT. It is difficult to detect the change of temperature and concentration in the growth cavity in real time, so it is necessary to use the numerical simulation method to study the process in advance in order to guide the actual production process. We find that the temperature gradient, operating pressure and surface temperature of seed crystal have important influence on the growth rate of the crystal. Specifically, with the increase of the temperature gradient in the growth cavity, Bi2Te3 thermoelectric materials are widely used because of their good thermoelectric properties at room temperature, but the thermoelectric materials in moderate temperature region contain Pb and other heavy metal elements. In the process of producing and using related thermoelectric devices, the environment will be adversely affected, so we hope to expand the applicable temperature range of Bi2Te3 thermoelectric materials. In the experiment of preparing Bi2Te3 bulk material with MA-PAS and measuring it in follow-up, we found that by adding S element into Bi2Te3, the thermoelectric properties of the material in the medium temperature region can be improved very well. Among them, Bi2Te2.5S0.5 shows the potential to be used at moderate temperature.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304

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