Hot electron collector current of the double barrier tunnel transistor

초록

Recently, Shottky-barrier based three terminal spin devices such as spin valve transistor (SVT) [1] and magnetic tunnel transistor (MTT) [2] have been developed. The collector current of these devices is related to the spin-dependent transport of hot electrons rather than electrons near the Fermi energy. The energy of the hot electrons is determined by the Schottky barrier height at the emitter or collector side of each device, and the collector current is very small. This disadvantage of small current in SVT and MTT is intrinsic, because the Schottky barrier height is material-dependent and can not be controlled by bias. Lee et al. [3] recently suggested an all metal-based double barrier tunnel transistor (DBTT) to overcome this difficulty with the Schottky barrier. In this paper, the properties of collector current of this new noble device will be investigated. The DBTT was fabricated with a structure of SiO2/Ta(5 nm)/NiFe(6 nm)/IrMn(8 nm)/CoFe(4 nm) [emitter] /AlOx(1.6 nm)/ NiFe(8 nm) [base] /AlOx(1.6 nm)/ CoFe(2 nm)/NiFe(6 nm)/IrMn(8 nm)/Ta(5 nm) [collector]. Each electrode was defined by multiple photolithography and Ar ion beam milling. Details of sample fabrication can be found in Ref. [3]. Each of bottom and top ferromagnetic layers is coupled to the neighboring antiferromagnetic IrMn layer. The NiFe(8 nm) layer in the middle works as a free layer which valves a spin-dependent current depending on the direction of applied fields. The amount of hot electron current is 5 nA, as noted in our previous work [3]. However, the current density is very high because the junction size of our DBTT is much smaller than those of conventional Schottky barrier based transistors.