Electrical Spin Injection and Detection in Mn₅Ge₃/Ge/Mn₅Ge₃ Nanowire Transistors

Abstract

In this Letter, we report the electrical spin injection and detection in Ge nanowire transistors with single-crystalline ferromagnetic Mn5Ge3 as source/drain contacts formed by thermal reactions. Degenerate indium dopants were successfully incorporated into as-grown Ge nanowires as p-type doping to alleviate the conductivity mismatch between Ge and Mn5Ge3. The magnetoresistance (MR) of the Mn5Ge3/Ge/Mn5Ge3 nanowire transistor was found to be largely affected by the applied bias. Specifically, negative and hysteretic MR curves were observed under a large current bias in the temperature range from T = 2 K up to T = 50 K, which clearly indicated the electrical spin injection from ferromagnetic Mn5Ge3 contacts into Ge nanowires. In addition to the bias effect, the MR amplitude was found to exponentially decay with the Ge nanowire channel length; this fact was explained by the dominated Elliot-Yafet spin-relaxation mechanism. The fitting of MR further revealed a spin diffusion length of l sf = 480 ± 13 nm and a spin lifetime exceeding 244 ps at T = 10 K in p-type Ge nanowires, and they showed a weak temperature dependence between 2 and 50 K. Ge nanowires showed a significant enhancement in the measured spin diffusion length and spin lifetime compared with those reported for bulk p-type Ge. Our study of the spin transport in the Mn5Ge3/Ge/Mn5Ge3 nanowire transistor points to a possible realization of spin-based transistors; it may also open up new opportunities to create novel Ge nanowire-based spintronic devices. Furthermore, the simple fabrication process promises a compatible integration into standard Si technology in the future.

Very low-temperature epitaxial growth of Mn5Ge3 and Mn5Ge3C0.2 films on Ge(111) using molecular beam epitaxy

“…Even though very recently spin transport has been demonstrated in Mn 5 Ge 3 /Ge/Mn 5 Ge 3 nanowires [7,8], spin transport in Mn 5 Ge 3 /Ge/Mn 5 Ge 3 thin films has to be studied. Because of the poor quality of germanium ox-…”

Growth of nanowire heterostructures and their optoelectronic and spintronic applications

“…Another important approach to fabricating axial nanowire heterostructures is through the solid-state reaction between a semiconductor nanowire and metal on contact that is deposited on top of the nanowire (Wu et al, 2004;Weber et al, 2006;Lin et al, 2008Lin et al, , 2010Tang et al, 2012Tang et al, , 2013. As an example, thermal annealing of an Si nanowire that is in contact with nickel (Ni) leads to the migration of Ni atoms into the wire, forming a NiSi alloy near the contact (Wu et al, 2004).…”

“…As an example, thermal annealing of an Si nanowire that is in contact with nickel (Ni) leads to the migration of Ni atoms into the wire, forming a NiSi alloy near the contact (Wu et al, 2004). Indeed, as discussed in more detail in Section 4.4, transistors based on Mn 5 Ge 3 /Ge/Mn 5 Ge 3 axial nanowires have shown promising electrical spin injection and detection primarily because of the atomically sharp interfaces (Tang et al, 2013). This type of axial heterostructure has been especially useful in spintronic device applications when the semiconductor-metal alloy is ferromagnetic.…”

Synthesis and characterization of nanostructured magnetoresistive Ni doped ZnO films

“…Origin of certain properties like ferromagnetism in nanostructured DMO's is still matter of discussion [12], hence the study of nanostructured DMO doped with TM could contribute to recognize these properties. Several studies are focused in semiconductors with magnetic characteristics at room temperature, to use their physico-chemical properties in realizing and to improve important devices like spin-LED [13], spin-transistors [14], logic devices [15] and magnetic memories (MRAM) [16].…”