  Ballistic hot electron transport overcomes the well-known problems of
conductivity and spin lifetime mismatch that plagues spin injection in
semiconductors with ferromagnetic ohmic contacts. Through the spin-dependent
mean-free-path, it also provides a means for spin detection after transport.
Experimental results using these techniques (consisting of spin precession and
spin-valve measurements) with Silicon-based devices reveals the exceptionally
long spin lifetime and high spin coherence induced by drift-dominated transport
in the semiconductor. An appropriate quantitative model that accurately
simulates the device characteristics for both undoped and doped spin transport
channels is described; it can be used to determine the spin current velocity,
diffusion constant, and spin lifetime, constituting a spin "Haynes-Shockley"
experiment without time-of-flight techniques. A perspective on the future of
these methods is offered as summary.
