Qualitative study of temperature-dependent spin signals in n-Ge-based lateral devices with Fe3Si/n+-Ge Schottky-tunnel contacts

Abstract

We study electrical spin injection and detection in n-Ge across Fe3Si/n+-Ge Schottky tunnel barriers. Spin-accumulation signals detected electrically by the three-terminal Hanle-effect measurements have large temperature dependence, and the spin signals disappear at around 200 K. We find that the temperature variation in the spin signals is strongly related to that in the interface resistance of the Fe3Si/n+-Ge contacts. We also observe marked reduction in nonlocal spin-valve signals with increasing temperature in the four-terminal device with almost the same Fe3Si/n+-Ge/n-Ge heterostructure. Note that the nonlocal spin signals depend on not only the measurement temperature but also on the electrical characteristics of the spin injector. Considering the results of three-terminal and four-terminal measurements, we conclude that temperature dependence of the spin signals in our Fe3Si/n+-Ge/n-Ge devices is governed by the electrical characteristics of the spin injector. This study means that it is necessary to consider the effective Schottky-tunnel contacts with the stability on temperature variations for next-generation Ge-based spintronic applications.

Room-temperature electrical creation of spin accumulation in n-Ge using highly resistive Fe3Si/n+-Ge Schottky-tunnel contacts

“…Three-terminal current-voltage (|I 21 | − V 23 ) characteristics for two different devices, which are called Device A and Device B, were measured at room temperature, together with that for a reference device in our previous works [19]. The |I 21 | − V 23 curves for both devices show asymmetric feature but the difference in the magnitude between |I 21 | in V 23 b 0 and |I 21 | in V 23 N 0 is less than one order at 300 K. This indicates that tunneling conduction of electrons is still dominant near room temperature.…”

“…In this paper, using the Fe 3 Si/n + -Ge Schottky tunnel barriers with a relatively high interface resistance compared to our previous works [18,19], we demonstrate room-temperature detection of spin accumulation in n-Ge. We will comment on the application of the Fe 3 Si/n + -Ge Schottky-tunnel contacts to the source and drain electrodes of Gebased spintronic devices.…”

“…Unfortunately, the detection of the spin signals was limited at low temperatures [18]. We found that the temperature dependent spin signal for our devices is strongly correlated with the temperature dependent interface resistance of the Schottky tunnel barrier [19]; the spin signals detected by the threeterminal Hanle-effect and nonlocal four-terminal measurements disappeared at higher temperature because the interface resistance was decreased with increasing temperature. To observe spin signals at room temperature, relatively high interface resistance compared to the above previous works may be required.…”

Progress towards Spin-Based Light Emission in Group IV Semiconductors

“…The results evidenced deviations from the diffusion model, possibly due to inhomogeneous doping distribution. A second work by Hamaya and coworkers [174] succeeded in observing evidence of spin accumulation in a similar structure without the Co layer. These investigations highlighted the importance of the interface and material quality to avoid uncontrolled fluctuations in the interface resistance, which may affect the magnitude of the spin accumulation in the semiconductor channel.…”

Finely Controlled Approaches to Formation of Heusler-Alloy/Semiconductor Heterostructures for Spintronics

“…19,[61][62][63] For electrical spin injection and detection in n-Ge, it is very important to understand the Schottky-tunnel contacts consisting of Heusleralloy/n-Ge interfaces. In general, electrical properties of such interfaces are dominated by the Fermi-level pinning phenomena [64][65][66] and doping conditions.…”