Analysis of GaAs Schottky/tunnel metal–insulator–semiconductor diode characteristics based on an interfacial layer model

Abstract

Current-voltage (I-V) characteristics of GaAs Schottky and tunnel metal–insulator–semiconductor diodes were measured at various temperatures between 100 and 400 K and analyzed on a basis of an interfacial layer model recently proposed by Maeda, Umezu, Ikoma, and Yoshimura [J. Appl. Phys. 68, 2858 (1990)]. The ideality factor n obtained from the forward I-V characteristics increased from about 1.05–1.1 to 2–3 as the temperature was decreased from 400 to 100 K. This could be interpreted as an increase in the electron occupation ratio of the interface states with decreasing temperatures. Precise measurement of the n value of the I-V curve revealed anomalous behavior as a function of the forward current, which was not observed in either amorphous or crystalline Si Schottky diodes. This seems to be related to the presence of a density peak in the interface state distribution like those proposed by Spicer, Newman, Spinat, Liliental-Weber, and Weber, [J. Vac. Sci. Technol. A 8, 2084 (1990)]. The interfacial Fermi level was demonstrated to move from the metal Fermi level as applied voltage is increased, but it hardly moved relative to the conduction band bottom. This is considered to be the first direct evidence of Fermi level pinning in I-V characteristics.