  We demonstrate fully electrical detection of spin injection in InAs quantum
wells. A spin polarized current is injected from a NiFe thin film to a
two-dimensional electron gas (2DEG) made of InAs based epitaxial multi-layers.
Injected spins accumulate and diffuse out in the 2DEG, and the spins are
electrically detected by a neighboring NiFe electrode. The observed spin
diffusion length is 1.8 um at 20 K. The injected spin polarization across the
NiFe/InAs interface is 1.9% at 20 K and remains at 1.4% even at room
temperature. Our experimental results will contribute significantly to the
realization of a practical spin field effect transistor.
