A comparative study of Schottky barrier height enhancement by realized pseudo-Schottky diodes on p-InP

In a metal/p-InP Schottky diode, interface states existing at the surface of the semiconductor are responsible for Fermi level pinning. The value of the Schottky barrier height contact is thus limited by this phenomenon. In gas sensor application, the sensitivity varies according to the Schottky barrier height. In order to reduce the effect of Fermi level pinning, we have developed pseudo-Schottky junctions on p-InP. The rectifying contact on p-InP using Ge-based metallization followed by moderate annealing temperatures is studied. Diffusion of Ge atoms at the metal–semiconductor interface creates a thin n+-InP layer. Pseudo-Schottky junctions are obtained with a significant barrier height enhancement, typically by 0.06 eV for Pd diodes and 0.12–0.14 eV for Au diodes. The metallization process involved throughout the present work leads to high-quality Schottky diodes within a rather simple procedure similar to those used in general to obtain good ohmic contacts. The behavior of pseudo-Schottky devices is thoroughly analyzed as a function of the annealing procedure. The best performances are obtained by applying cumulative annealing sequences, increasing the temperature while decreasing the time of thermal treatment. Comparisons of electrical characteristics between Au and Pd pseudo-Schottky diodes are realized.