Nature of forward and reverse saturation currents in metal—semiconductor contacts with the Schottky barrier

Abstract

The heavy dependence of the saturation currents for the forward and reverse I–V characteristics of high-barrier (>0.6 V) metal-semiconductor cont acts with the Schottky barrier on their diameter D is determined by an additional electric field formed under the effect of the contact periphery; this field is built into and codirected with the intrinsic electric field of the contact. It prevents the motion of electrons through the contact when a forward bias is applied across it. An increase in contact diameters from 5 to 700 µm results in decreasing the difference in forward and reverse saturation currents from five orders of magnitude to almost zero. The increase in the contact diameter, thus, results in decreasing periphery effect and absolute value of the built4n electric field. Adecrease in the barrier height( ≤0.6 V for D = 5 µm) also results in almost complete coincidence of forward and reverse saturation currents. At the reverse portions of the I–V characteristics, the effect of the built-in field manifests itself in a significant decrease in the effective height of the potential barrier due to a decrease in its width near the top and the substantial increase in the field electron emission through the barrier for lower energies. At the forward portions, it manifests itself in almost complete absence of the forward currents at low biases.