Electrical Properties of Nanometer-Sized Schottky Contacts on n-GaAs and n-InP Formed by in Situ Electrochemical Process

The current transport characteristics of nanometer-sized Schottky contacts were investigated from theoretical and experimental viewpoints. A theoretical calculation of the three dimensional (3D) potential distributions showed that the potential shape underneath the nano-Schottky contacts was considerably modified by the surface Fermi level pinning on the air exposed free surfaces, producing a saddle point in the potential. The current–voltage (I–V) curves were strongly influenced by this saddle point potential and resulted in nonlinear log I–V characteristics. Experimentally, the Pt nano-particles were selectively formed using the in situ electrochemical process on n-type GaAs and n-type InP substrates patterned using electron-beam (EB) lithography. Their I–V measurements were carried out using an atomic force microscopy (AFM) system equipped with a conductive probe. The log I–V curves of the nano-Schottky contacts showed nonlinear characteristics with large n values of 1.96 for n-GaAs and 1.27 for n-InP and could be very well explained by the theoretical I–V curves considering the "environmental" Fermi level pinning.