半导体硅和锗的磁电阻性能研究和应用

发布时间：2018-08-05 11:36

【摘要】：磁电阻效应是指材料在外加磁场下电阻发生变化的现象,基于磁电阻效应的器件已经广泛应用于计算机、电动车辆、磁性存储、航空航天、地磁检测等领域。本论文系统研究了半导体硅材料、锗材料的磁电输运性能和相关的物理机制,以期推进并拓宽这两种材料在磁传感领域的应用。首先,我们制备了两电极硅基器件(Al/Ti/n+-Si/n-Si),发现器件的I-V曲线在临界电压下会出现电压跳变现象,使器件由高阻态变为低阻态;而磁场会导致此临界电压值增加,故在高低阻值过渡区间内得到优异的室温磁电阻性能(0.07 T下MR=2450%,0.1 T下MR=2520%)。即使在7 T高磁场下,磁阻也未出现饱和的迹象(7 T下MR=7400%),这种大磁阻效应和S型微分负电导引起的电流细丝效应有关。此外,适当的增加电极间距、宽度或降低实验温度,都可以使器件的磁阻值得到增强。当温度为100 K时,磁电阻在7.65 V和0.05 T下可达2010%。其次,我们制备了两电极的In/Ge/In器件,并系统研究了器件的磁电输运性能。随着外加电压的增加,电输运机制由线性的欧姆传导机制,变为非线性的空间电荷传导机制;当电压继续增加时,会引发局部碰撞电离过程。进一步研究发现,当磁场方向平行于样品表面且垂直于电流方向时,可通过控制磁场的正负来选择载流子的复合表面,获得非对称的磁电阻效应。通过几何尺寸和复合表面的优化,器件在低磁场(0.1 T下MR=80%、0.05 T下MR=40%)和高磁场(7 T下MR=6300%)都展示了优异的磁电阻性能;且当B4 T时,磁阻和磁场呈线性依赖关系,这种线性度甚至可以维持到50 mT。再次,利用锗单晶的表面非对称性和大磁电阻效应,我们设计出一种由电压和磁场控制的可编程逻辑器件,并在室温下实现COPY、NOT、AND、OR、NAND和NOR逻辑运算。锗基逻辑器件提供了一种从晶体管逻辑电路向磁场控制的逻辑电路的范例转换,具有结构简单、逻辑输出信噪比高、工作电场低等优点。最后,借助二极管增强了四电极锗基器件的室温磁电阻。实验发现,增加器件的几何尺寸(W/L)或二极管伏安特性的“陡峭”程度,都能使磁电阻值得到进一步的增强。室温下1.2 T时,其磁电阻值高达3×104%,且相应的低磁场灵敏度在0.02 T下为200%。该研究为室温磁传感器件,尤其是低磁场下的半导体磁传感器件提供了新的思路。
[Abstract]:The magnetoresistance effect refers to the change of the resistance of the material under the applied magnetic field. The devices based on the magnetoresistance effect have been widely used in the fields of computer, electric vehicles, magnetic storage, aeronautics and Astronautics, and geomagnetic detection. In this paper, the magnetic and electrical transport properties and related physical mechanisms of semiconductor silicon materials and germanium materials are systematically studied in this paper. To advance and broaden the application of these two materials in the field of magnetic sensing. First, we have prepared a two electrode silicon based device (Al/Ti/n+-Si/n-Si). It is found that the I-V curve of the device will appear voltage jump under the critical voltage to make the device change from high resistance state to low resistance state, and the magnetic field will lead to the increase of the critical voltage value, so in the high and low transition zone Excellent room temperature magnetoresistance (under 0.07 T MR=2450%, 0.1 T under MR=2520%). Even in a 7 T high magnetic field, the magnetoresistance does not appear to be saturated (7 T MR=7400%). This large magnetoresistance effect is related to the current filaments caused by S differential negative conductance. In addition, the appropriate increase in electrode spacing, width or decrease the experimental temperature, The magnetoresistance of the device is worth increasing. When the temperature is 100 K, the magnetoresistance can reach 2010%. under 7.65 V and 0.05 T. We have prepared the In/Ge/In device of the two electrode and systematically studied the magnetic and electrical transport properties of the device. It is found that when the direction of the magnetic field is parallel to the surface of the sample and perpendicular to the direction of the current, the compound surface of the carrier can be selected by controlling the positive and negative of the magnetic field to obtain the asymmetric magnetoresistance effect. The advantages of the geometric size and the composite surface can be obtained. In the low magnetic field (0.1 T MR=80%, 0.05 T under MR=40%) and high magnetic field (7 T MR=6300%), the excellent magnetoresistance performance is displayed; and when B4 T, the magnetoresistance and magnetic field are linear dependence, and the linearity can be maintained to 50 mT. again. Using the surface asymmetry and large magnetoresistance effect of the germanium single crystal, we design a kind of a kind of magnetic resistance effect. A programmable logic device controlled by a voltage and magnetic field and a logical operation of COPY, NOT, AND, OR, NAND and NOR at room temperature. The germanium based logic device provides an example conversion from a logical circuit controlled by a transistor logic circuit to a magnetic field. It has the advantages of simple structure, high signal to noise ratio and low working electric field. Finally, with the aid of two The pole tube enhanced the room temperature magnetoresistance of the four electrode germanium based devices. It was found that increasing the geometric size (W/L) of the device or the "steep" degree of the diode volt ampere characteristics could make the magnetoresistance worth further enhancement. At 1.2 T at room temperature, the magnetoresistance value was up to 3 * 104%, and the corresponding low magnetic field sensitivity was under 0.02 T for the study. It provides a new idea for room temperature magnetic sensors, especially semiconductor magnetic sensors under low magnetic field.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN304.1

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