Abstract: 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.
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