Fermi level depinning of Ge Schottky contacts using single crystalline MgO

The authors investigated the origin of FL pinning in Ge Schottky junctions by characterizing the Fe/MgO/n-Ge junctions with single-crystalline and atomically smooth MgO epitaxially grown on Ge. The weak dependence of the SBH on the MgO thickness suggests that the surface states due to native defects on the Ge surface are likely to play the dominant role in the FL pinning. Further evidence is given by the fact that passivating the surface dangling bonds with aqueous (NH₄)₂S solution depins the FL more effectively than inserting the MgO films, which would have been the opposite if MIGS were to play the dominant role.