Development of the spin-valve transistor

As the easiest experimental approach, GMR (giant magnetoresistance) is usually measured using the current in plane (CIP)-GMR. The spin-valve transistor has previously been presented as a spectroscopic tool to measure current perpendicular to the planes (CPP)-GMR. Hot electrons cross the magnetic multilayer base quasi-ballistically and the number reaching the collector depends exponentially on the perpendicular hot electron mean free path. Collector current changes of 390% at 77 K have already been measured. Apart from the substantial fundamental value, such properties may be useful for sensor applications. The electron energy range fills the gap between the Fermi surface transport in resistance measurements and other hot electron techniques such as spin polarised electron energy loss spectroscopy (SPEELS). The preparation problem of the spin-valve transistor and metal base transistor structures in general, the deposition of a device quality semiconductor on top of a metal, has now been tackled by bonding of two semiconductor substrates during vacuum deposition of a metal: an excellent bond is achieved at room temperature. TEM photos show a continuous buried metal film. Apart from preparation of various metal base transistor like structures, many other fields may benefit form this new technique.