Large spin accumulation voltages in epitaxialMn5Ge3contacts on Ge without an oxide tunnel barrier

Abstract

Spin injection in high-quality epitaxial Mn 5 Ge 3 Schottky contacts on n-type Ge has been investigated using a three-terminal Hanle effect measurement. Clear Hanle and inverted Hanle signals with features characteristic of spin accumulation and spin precession are observed up to 200 K. Strikingly, the observed spin voltage is several orders of magnitude larger than predicted by the theory of spin injection and diffusive spin transport. Since the devices have no oxide tunnel barrier, the discrepancy between theory and experiments cannot be explained by the often-invoked spin accumulation in localized states associated with the oxide or oxide/semiconductor interface. The observed spin voltages therefore must originate from the Ge itself, either from spins in the Ge bulk bands or its depletion region.

Electrical detection of spin-polarized current in topological insulator Bi1.5Sb0.5Te1.7Se1.3

“…for BST 17 The difference might be caused by the localized spin states at the tunnel barrier, [36][37][38] accumulation of bulk carriers at the BSTS/Co tunnel contact interface owing to the Fermilevel pinning, 39 non-ideal spin-detection efficiency of the considered tunnel contact 20 , material quality of the considered BSTS flakes, etc. Nevertheless, the obtained value is larger than those reported in other studies ( = 0.005~0.01 15,20 ) using BSTS and permalloy electrode, which has work function in the range of 4.80 to 4.83 eV.…”

Nonlinear spin transport in a rectifying ferromagnet/semiconductor Schottky contact

“…With this in mind, a recent experiment 51 has focused on a direct Schottky contact of a metallic ferromagnet (Mn 5 Ge 3 ) and a semiconductor (Ge), in which the absence of a tunnel oxide eliminates all sources of spin signal enhancement that rely explicitly on localized states associated with the oxide [14][15][16]30,44,45 . Nevertheless, the observed spin signals 51 , that have all the characteristic features of spin accumulation and spin precession due to the Hanle effect, were found to be up to 4 orders of magnitude larger than predicted by linear transport models [7][8][9][10][11] . Since the studied Mn 5 Ge 3 /Schottky contacts exhibited highly rectifying current-voltage characteristics, the question arises whether the non-linear transport can affect the spin signal magnitude.…”

Progress towards Spin-Based Light Emission in Group IV Semiconductors

“…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. The use of MnGe later on enabled the observation of large voltages, heralding successful spin accumulation, and the measurement of a significant figure of merit, such as a spin-resistance-area product (spin-RA) of ≈100 Ω·µm 2 up to 200 K [175]. The clear-cut evidence of electrical spin injection using DMS was given by Kasahara and coworkers in [176].…”