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The Topological Insulator (TI) BiSb, grown with a (012) film texture using molecular beam epitaxy, and coupled with a FM layer has been shown to have a very high Spin Hall Angle (SHA) > 2 and high electrical conductivity (>10 5 Ohm -1 m -1 ) in thin film stacks 1 . This makes the TI material ideally suited for spin transfer devices requiring several orders of magnitude less power consumption to operate than other traditional devices 2 . However, the practical implementation of this TI material into devices using PVD requires you overcome many severe material challenges. The BiSb material is very soft, easily damaged in ion milling or by subsequent depositions, it has a very low melting point ~ 280C, and hence possesses a very large in-plane grain size as deposited at room temperature, ~6X the targeted thickness in devices. Thermal Migration of Sb out of the TI material is also a severe problem, which is exacerbated by film roughness and large grain sizes, and all of this must be solved while growing and maintaining a non-prismatic (012) texture of BiSb with low roughness, good interfacial TI properties, at reasonable operating temperatures > 180C in actual device stacks, non-epitaxially on SiOx or ceramic substrates. We discuss here how we addressed these challenges through appropriate selection of epitaxial and non-epitaxial materials for buffer layer(s) (bottom interface), and (top interface) interlayer(s), and by using a non-uniform thickness doping of the BiSb(X) material to stabilize and grow a BiSbX(012) textured layer with low roughness, good TI properties, at elevated temperatures in FM thin film stacks.

Spin bipolar transistors (SBTs) with spin dependent output characteristics can be applied to non-volatile memory cells and reconfigurable logic circuits. III-V based carrier-induced ferromagnetic semiconductors (FMSs) are suitable materials for realizing SBTs, because they are compatible with non-magnetic III-V semiconductors with respect to the crystal structure and conductivity. In particular, Fe-based FMSs are promising materials for SBTs because both p-type and n-type FMSs are available and their ferromagnetism is maintained at room temperature. In this study, we fabricated spin bipolar transistors using a (Ga, Fe)Sb/(In, Fe)As p-n junction on top of a p-n-p AlGaAs/GaAs heterojunction bipolar transistor structure, grown by molecular beam epitaxy. We obtained the modulation of the collector current by the base voltage and the magnetoresistance (MR) effect. The bias dependence and temperature dependence of MR suggest that the observed MR signal is likely to originate from the spin-valve effect at the ferromagnetic (Ga, Fe)Sb/(In, Fe)As p-n junction. Our results indicate that Fe-based FMSs are promising for semiconductor spintronics devices.

We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga 1−x ,Fe x )Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy (LT-MBE). Our crystal structure analysis by scanning transmission electron microscopy (STEM) indicates that the (Ga 1−x ,Fe x )Sb thin films maintain the zinc-blende crystal structure at x = 25%. The intrinsic ferromagnetism was confirmed by magnetic circular dichroism (MCD) spectroscopy and anomalous Hall effect (AHE) measurements. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III–V ferromagnetic semiconductors.

Introducing spin degrees of freedom into the present semiconductor electronics is a very important issue for realizing novel devices which will be needed in the future information technology. For fabricating such devices, it is necessary to exploit and fabricate semiconductor-based magnetic materials. III-V-based ferromagnetic semiconductors and MnAs/III-V hybrid nanostructures are hopeful candidates and model systems for future spintronic devices [1, 2].

A 1540 nm, TM mode waveguide isolator based on the nonreciprocal loss shift was developed. It consisted of a semiconductor waveguide with a ferromagnetic MnAs layer and showed an isolation ratio of 8.8 dB/mm.