Transport properties and spin accumulation in semiconductor two-dimensional electron gas/superconductor junctions

We extend the Blonder–Tinkham–Klapwijk (BTK) theory to study transport properties of semiconductor two-dimensional electron gas (2DEG)/superconductor junctions, including the Rashbar spin–orbit interaction in a 2DEG of finite width. The effects of Rashba spin–orbit interaction on the conductance are investigated, and a reduction of this conductance is found. A couple of well known results for quantized conductance are verified. Moreover, the averaged spin value and shape of spin fluctuation in the 2DEG are calculated. It is found that the y-component of the spin (Sy) is even, while the x- and z-components are odd, with respect to the propagating mode index. Consequently, Sx and Sz are summed up to vanish, while Sy accumulates to a finite value. Sy is explicitly given and a spin-polarization in the y-direction is found in the 2DEG near the interface.