Diluted Magnetic Semiconductor Based Memory Devices

为了评估基于铁磁稀磁半导体（DMS’s）的存储器件的可行性，对III-V型铁磁稀磁半导体（DMS’s）及其加工工艺、存储器件结构进行了研究。得到了以下结果：(1)利用低温分子束外延（MBE）技术首次合成了以GaAs， （Ga, Mn）As为基材的新型III-V基铁磁DMS。最大Mn摩尔分数为0.071。x射线衍射研究表明，晶格常数随Mn摩尔分数的增加而增加（维加德定律）。由于这种材料可以很容易地与现有的III-V电路集成，因此它可能适用于存储器应用。(2)磁化和磁输运测量表明（Ga, Mn） as具有铁磁性；目前获得的最高居里温度为110K。居里温度在0.05以下与Mn摩尔分数成正比。(3)利用InGaAs缓冲层反转（Ga, Mn）As中的应变方向，可以使易轴垂直于样品平面。这对于利用异常霍尔效应读取存储在存储器中的信息的存储器应用是非常重要的。(4)从临界散射和居里温度出发，发现铁磁性的来源是RKKY相互作用。(5)开发了存储器制造的加工技术，并制作了存储器元件，研究其应用潜力。

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.