11:00 〜 11:15
▼ [20a-D104-8] Large anisotropic magnetoresistance induced by a proximity effect in an InAs / (Ga,Fe)Sb quantum well heterostructure
キーワード：Ferromagnetic Semiconductor, Semiconductor heterostructure, Magnetoresistance
Fe doped narrow-gap III-V ferromagnetic semiconductor (FMSs), InFeAs, GaFeSb, InFeSb, are promising materials, because Fe atoms are in the neutral state thus do not supply carriers but only local spins in III-V semiconductors, so we can realize both n and p-type and their Curie temperatures can be over room temperature [1,2]. Meanwhile, InAs / GaSb heterostructures have some novel properties; staggered bands, little lattice mismatch (~0.6%), and high electron mobility. In the heterostructure of an InAs quantum well with a GaFeSb barrier, the in-plane transport shows the unique magnetoresistance (MR) originated from the scattering of s electrons in InAs as a non-ferromagnet layer with d electrons from the magnetization of GaFeSb at the InAs/GaFeSb interface. Note that the resistance of InAs is much lower than that of GaFeSb by more than two orders of magnitude. Therefore, the carriers flow only in the InAs layer. In this study, we observe this MR and modulate it by applying a gate voltage.
We have grown InAs (15 nm) / GaFeSb (15 nm, Fe 20%) / AlSb (300 nm) / AlAs (15 nm) / GaAs (100 nm) on semi-insulating GaAs (001) substrates by low temperature molecular beam epitaxy. This sample was patterned into a 100 x 200 μm2 Hall bar; HfO2 was deposited for a gate insulating layer by atomic layer deposition; the Au gate electrode was fabricated (Fig. 1(b)). In the measurement, we applied the gate voltage from the gate pad to the source electrode and measured the MR by the four terminal method. The magnetic field H (= 1 T) angle direction dependence of the resistance when the current JDS = 4.3 μA and the gate voltage Vg = 0 V at 3.5 K. H was rotated (in the y-z plane) as it was always perpendicular to JDS (// x axis), and 0° and 90° means perpendicular to the film plane and in the film plane, respectively. The MR ratio is 2.7%, which is large compared with another study about the in-plane transport of ferromagnet / non-ferromagnet [3][4]. This result means that the electron wavefunction in the InAs penetrates into the GaFeSb even at Vg = 0 V and it is the origin of the anisotropy of the MR. Then, we applied Vg and the MR ratio reaches 7.8 % when Vg = -3 V. We can successfully control the electron wavefunction and enhance the MR in the InAs/GaFeSb heterostructure. In addition, the JDS vs. source-drain voltage VDS shows the transistor behavior, which means JDS is greatly modulated by Vg, and finally we confirmed that this device behaves like a magnetic transistor.
We have grown InAs (15 nm) / GaFeSb (15 nm, Fe 20%) / AlSb (300 nm) / AlAs (15 nm) / GaAs (100 nm) on semi-insulating GaAs (001) substrates by low temperature molecular beam epitaxy. This sample was patterned into a 100 x 200 μm2 Hall bar; HfO2 was deposited for a gate insulating layer by atomic layer deposition; the Au gate electrode was fabricated (Fig. 1(b)). In the measurement, we applied the gate voltage from the gate pad to the source electrode and measured the MR by the four terminal method. The magnetic field H (= 1 T) angle direction dependence of the resistance when the current JDS = 4.3 μA and the gate voltage Vg = 0 V at 3.5 K. H was rotated (in the y-z plane) as it was always perpendicular to JDS (// x axis), and 0° and 90° means perpendicular to the film plane and in the film plane, respectively. The MR ratio is 2.7%, which is large compared with another study about the in-plane transport of ferromagnet / non-ferromagnet [3][4]. This result means that the electron wavefunction in the InAs penetrates into the GaFeSb even at Vg = 0 V and it is the origin of the anisotropy of the MR. Then, we applied Vg and the MR ratio reaches 7.8 % when Vg = -3 V. We can successfully control the electron wavefunction and enhance the MR in the InAs/GaFeSb heterostructure. In addition, the JDS vs. source-drain voltage VDS shows the transistor behavior, which means JDS is greatly modulated by Vg, and finally we confirmed that this device behaves like a magnetic transistor.