Diluted Magnetic Semiconductor Based Memory Devices

为了评估基于铁磁稀磁半导体(DMS)的存储器件的可行性，对基于III-V铁磁稀磁半导体(DMS)的存储器件的工艺、存储器件结构进行了研究。(1)首次用低温分子束外延(MBE)方法合成了以(Ga，Mn)As为基础的III-V系铁磁DMS。最大锰摩尔分数为0.071。X-射线衍射分析表明，晶格常数随Mn摩尔分数的增加而增大(Vegard定律)。这种材料可以很容易地与现有的III-V电路集成在一起。(2)磁化和磁输运测量表明(Ga，Mn)As是铁磁性的，到目前为止获得的最高居里温度为110K。居里温度与低于0.05的Mn摩尔分数成正比。(3)用InGaAs缓冲层反转(Ga，Mn)As的应变方向，表明易轴可以垂直于样品平面。这对于利用反常霍尔效应来读取存储在存储器中的信息的存储应用是非常重要的发现。(4)从临界散射和居里温度发现，铁磁性的起源是RKKY相互作用。(5)发展了存储器的制造工艺，并制作了存储元件，以研究其应用的潜力。

In order to asses the feasibility of memory devices based on ferromagnetic diluted magnetic semiconductors (DMS's)'study on III-V based ferromagnetic DMS's, its processing technology, memory devices structures has been carried out. The following results have been obtained.(1)New III-V based ferromagnetic DMS based on GaAs, (Ga, Mn)As, has been synthesized for the first time by low temperature molecular beam epitaxy (MBE). Maximum Mn mole fraction was found to be 0.071. X-ray diffraction study showed increase of lattice constant with increase of Mn mole fraction (vegard's law). This material may be suitable for the memory application since it can be easily integrated with existing III-V circuity.(2)Magnetization as well as magnetotransport measurements showed that (Ga, Mn)As is ferromagnetic ; the highest curie temperature so far obtained was 110K.Curie temperature is proportional to Mn mole fraction below 0.05.(3)Reversing the strain direction in (Ga, Mn)As by using InGaAs buffer layrs, it was shown that the easy axis can be made perpendicular to the sample plane. This is very important finding for the memory application using anomalous Hall effect for reading the information stored in memory.(4)From critical scattering and Curie temperature, it was found that the origin of ferromagnetism is RKKY interaction.(5)Processing technology for memory fabrication has been developed and memory elements were fabricated to study its potential for applicaitons.