Introduction to Spin-Polarized Ballistic Hot Electron Injection and Detection in Silicon

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.