Electrical injection and detection of spin accumulation in Ge at room temperature

Abstract

We inject spin-polarized electrons from an Fe/MgO tunnel barrier contact into n-type Ge(001) substrates with electron densities 2e16 < n < 8e17 cm-3, and electrically detect the resulting spin accumulation using three-terminal Hanle measurements. We observe significant spin accumulation in the Ge up to room temperature. We observe precessional dephasing of the spin accumulation (the Hanle effect) in an applied magnetic field for both forward and reverse bias (spin extraction and injection), and determine spin lifetimes and corresponding diffusion lengths for temperatures of 225 K to 300 K. The room temperature spin lifetime increases from τs = 50 ps to 123 ps with decreasing electron concentration, as expected from electron spin resonance work on bulk Ge. The measured spin resistance-area product is in good agreement with values predicted by theory for samples with carrier densities below the metal-insulator transition (MIT), but 100x larger for samples above the MIT. These data demonstrate that the spin accumulation measured occurs in the Ge, although dopant-derived interface or band states may enhance the measured spin voltage above the MIT. We estimate the polarization in the Ge to be on the order of 1%.

arXiv comment14 pages, 4 figures

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• Non-linear spin transport in a rectifying ferromagnet/semiconductor Schottky contact
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• On the origin of the giant spin detection efficiency in tunnel barrier based electrical spin detector
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• Spin transport and accumulation in the persistent photoconductor Al${}_{0.3}$Ga${}_{0.7}$As
• Triggering phase-coherent spin packets by pulsed electrical spin injection across an Fe/GaAs Schottky barrier
• Lateral Mn5Ge3 spin-valve in contact with a high-mobility Ge two-dimensional hole gas
• Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals