Experimental Aspects of Tunneling in Metal-Semiconductor Barriers

Abstract

The electrical characteristics of diodes made from degenerate n‐type Ge with either Au or In as the metallic element are reported. The results support a previously published calculation [Phys. Rev. 150, 466 (1966)]. It is significant that the observation can be interpreted quantitatively. Data are presented in terms of the dependence of incremental resistance dv/di or conductance di/dv on applied voltage. Maxima in the incremental resistance predicted to occur at an applied voltage which corresponds to the Fermi degeneracy of the n‐type Ge are observed. Data for several values of impurity, density, and temperature are shown to correspond quantitatively with the prediction. However, evidence suggests the importance of band tailing, a feature not included in the calculation. Observation of several additional effects is also reported. Pronounced structure near zero bias appears when the metallic element is in the superconducting state. This is well described by the BCS theory. The threshold for tunneling into the conduction‐band minimum Γ_2′ was also observed. From this the separation in energy with respect to the L‐band minima is determined to be Γ_2′−L=0.154±0.003 eV. Anomalous structure at zero bias similar to that observed by others in p‐n junctions and metal‐oxide‐metal structures is reported but not interpreted.