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Study on spin device characteristic having p-n-p structure using GeTe based ferromagnetic semiconductors

使用GeTe基铁磁半导体的p-n-p结构自旋器件特性研究

基本信息

批准号：
18560306
负责人：
ASADA Hironori
金额：
$ 2.44万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

We have studied on the growth of GeTe based ferromagnetic semiconductors by molecular-beam epitaxy (MBE) method and fabrication of ferromagnetic tunnel junction (MTJ), and obtained the following results.1. It was found that the crystallinity and magnetic properties of GeTe based ferromagnetic semiconductors strongly depended on Te/magnetic ion flux ratio. It was confirmed that crystallinity of the film on a SrF_2 substrate was better than that on a BaF_2 substrate. The obtained Curie temperatures were 200 K for Ge_<1-x>Mn_XTe with x=008 and 190 K for Ge_<1-x>Cr_XTe with x=0.07, respectively.2. MTJs having p-n-p structure using n-type semiconductor CdS barrier were grown by ICB method and the tunnel current was observed for MTJ with CdS barrier thickness of 3.4 nm. The estimated barrier height using Simmons equation was 0.28 eV which was quite small compared to the designed value (2.1 eV). However, tunnel magnetoresistance was not obtained. MTJs were also grown by MBE and successfully obtained GeTe/GeMnTe/CdS/GeMnTe epitaxial films.3. MTJs with barrier layer of p-type semiconductor ZnTe, ferromagnetic insulator EuS and SrF_2 were fabricated. Epitaxial growth on a BaF2 substrate by using MBE method was confirmed in both multilayers with ZnTe and EuS barrier layers. Magnetoresistance ratio of 4.2 % at 10 K was obtained in the GeTe/GeMnTe/EuS(2 nm)/GeTe structure. The estimated barrier thickness from I-V characteristics using Simmons equation agreed well with the designed value and the barrier heights were 0.88-1.07 eV.

我们对GeTe基铁磁半导体材料的分子束外延（MBE）生长和铁磁隧道结（MTJ）的制备进行了研究，取得了以下成果.结果表明，GeTe基铁磁半导体的结晶度和磁性能与Te/磁离子通量比密切相关。结果表明，在SrF_2衬底上的薄膜结晶度优于BaF_2衬底上的薄膜结晶度。Ge_<1-x>Mn_XTe（x=008）的居里温度为200 K，Ge_<1-x>Cr_XTe（x=0.07）的居里温度为190 K.采用ICB方法生长了具有p-n-p结构的MTJ，并在CdS势垒厚度为3.4nm时观察到了隧道电流。使用Simmons方程估计的势垒高度为0.28 eV，与设计值（2.1 eV）相比相当小。然而，隧道磁阻没有得到。利用分子束外延生长了MTJ，成功地获得了GeTe/GeMnTe/CdS/GeMnTe外延薄膜.制备了势垒层为p型半导体ZnTe、铁磁绝缘体EuS和SrF_2的MTJ。通过使用MBE方法在BaF 2衬底上的外延生长被证实在这两个多层与ZnTe和EuS阻挡层。GeTe/GeMnTe/EuS（2 nm）/GeTe结构在10 K时的磁电阻率为4.2%.利用Simmons方程估算的势垒厚度与设计值吻合较好，势垒高度为0.88- 1.07eV。