Spin Accumulation in Nondegenerate and Heavily Doped p-Type Germanium

Abstract

Spin accumulation induced in p-type germanium from Fe/MgO tunnel contacts is\nstudied as a function of hole concentration p (10^16 - 10^19 cm-3). For all p,\nthe contacts are free of rectification and Schottky barrier, guaranteeing spin\ninjection into the Ge and preventing spin accumulation enhancement by two-step\ntunneling via interface states. The observed spin accumulation is smallest for\nnondegenerate doping (p ~ 10^16 cm-3) and increases for heavily doped Ge. This\ntrend is opposite to what is expected from spin injection and diffusion theory.\nFor heavily doped Ge, the observed spin accumulation is orders of magnitude\nlarger than predicted.\n