锗基半导体器件的界面磁阻效应和体磁阻效应

Interface Magnetoresistance Effect and Bulk Magnetoresistance Effect of Germanium-based Semiconductor Devices

本工作对Ag/p-Ge∶Ga/Ag器件的界面磁阻和体磁阻效应进行了研究,结果表明该器件的体磁阻效应远大于界面磁阻效应。对界面磁阻而言,界面局部等离子体的形成与淬灭受外加磁场的影响较小,致使界面磁阻很小;而对体磁阻而言,磁场导致载流子复合速率加快,使载流子浓度急剧下降,从而导致体磁阻数值较大。进一步研究发现,采用低载流子浓度Ge制备的器件可以获得更为优异的体磁阻效应。本工作也研究了不同磁场施加方向对体磁阻效应的影响,发现低温时体磁阻具有明显的各向异性。当温度低于200 K时,垂直方向的体磁阻明显大于平行方向的体磁阻,其中当温度为10 K时,垂直方向体磁阻最大值约为123%@1 T,远大于平行方向的体磁阻数值(仅约为41%@1 T)。机理分析认为,体磁阻效应的各向异性源于不同磁场构型下几何效应的差异,而低温下载流子迁移率的增加导致这种几何效应的影响更为明显。

In this work,the interface and bulk MR of the Ag/p-Ge∶Ga/Ag device were investigated.The results show that the bulk MR is much larger than the interface MR.For the interface MR effects,the applied magnetic fields have little influence on the formation and quenching of the local plasma at the interface of Ag/p-Ge∶Ga,leading to a small interface MR.For the bulk MR effects,the carrier recombination rate is accelera-ted under the applied magnetic fields,and then the carriers concentration decreases sharply,resulting in a large MR value.Further study finds that the germanium-based semiconductor device with low carrier concentration is beneficial for obtaining an excellent bulk MR effect.We also studied the effect of different magnetic field orientations on the bulk MR,and find that the bulk MR become more anisotropic at lower temperature.When T<200 K,the values of bulk MR in the perpendicular orientation are much larger than that of in the parallel orientation.For example,when T=10 K,the largest value of bulk MR in the perpendicular orientation is about 123%@1 T,which is much larger than 41%@1 T in the parallel orie-ntation.Mechanism analysis indicates that the anisotropic characteristics is derived from the geometric effect which is enhanced due to the high carrier mobility characteristic at low temperature.