Spin transport in non-degenerate semiconductors is expected to pave a way to the creation of spin transistors, spin logic devices and reconfigurable logic circuits, because room temperature (RT) spin transport in Si has already been achieved. However, RT spin transport has been limited to degenerate Si, which makes it difficult to produce spin-based signals because a gate electric field cannot be used to manipulate such signals. Here, we report the experimental demonstration of spin transport in non-degenerate Si with a spin metal-oxide-semiconductor field-effect transistor (MOSFET) structure. We successfully observed the modulation of the Hanle-type spin precession signals, which is a characteristic spin dynamics in non-degenerate semiconductor. We obtained long spin transport of more than 20 µm and spin rotation, greater than 4π at RT. We also observed gate-induced modulation of spin transport signals at RT. The modulation of spin diffusion length as a function of a gate voltage was successfully observed, which we attributed to the Elliott-Yafet spin relaxation mechanism. These achievements are expected to make avenues to create of practical Si-based spin MOSFETs.

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The authors identified an insufficient description in the caption of Fig. 3(a) of the main text about subtracting a background signal to obtain the Hanle spin signals [ Fig. 3(a)]. The detailed procedure is as follows: The background signal was defined as a signal that was independent of magnetization alignments, i.e., parallel and antiparallel. The background signal V BG ðBÞ was calculated to be ½V P ðBÞ þ V AP ðBÞ=2, where V P ðBÞ and V AP ðBÞ are Hanle spin signals under parallel and antiparallel magnetization configurations, under the assumption that the background signal is unchanged. The authors P Ω AP 300 K

A large spin-accumulation voltage of more than 1.5 mV at 1 mA, i.e., a magnetoresistance of 1.5  was measured by means of the local three-terminal magnetoresistance in nondegenerate Si-based lateral spin valves (LSVs) at room temperature. This is the largest spin-accumulation voltage measured in semiconductor-based LSVs. The modified spin drift-diffusion model, which successfully accounts for the spin drift effect, explains the large spin-accumulation voltage and significant bias-current-polarity dependence. The model also shows that the spin drift effect enhances the spin-dependent magnetoresistance in the electric two terminal scheme. This finding provides a useful guiding principle for spin metal-oxide semiconductor field-effect transistor (MOSFET) operations.

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