Dependence of Electrical Properties of Ni/n-GaP/Al Schottky Contacts on Measurement Temperature and Thermal Annealing

Abstract

Ni/n-GaP/Al Schottky diodes have been fabricated and thermally annealed at 400 degrees C to obtain Schottky rectifying contacts with optimum performance and improve understanding of the effect of thermal annealing and the measurement temperature (MT) on their electrical characteristics. The measurement temperature was varied from 100 K to 400 K in steps of 20 K to determine the current-voltage (I-V) characteristics of the unannealed (as-deposited) and annealed diodes. The values of the barrier height (BH), ideality factor n, and Richardson constant of both diodes were determined by using the thermionic emission (TE) current equations. The results revealed that the BH of the annealed diode was higher than that of the as-deposited diode in the measurement temperature range of 260 K to 400 K; that is, a barrier modification by approximately 0.14 eV was observed. A greater series resistance R-s was obtained for the as-deposited than annealed diode at each temperature, except 140 K. This increase of R-s can be attributed to diffusion of Ni atoms into the GaP substrate due to the annealing at 400 degrees C. The abnormalities in the diode parameters were successfully explained by TE current equations modified according to a Gaussian distribution of the temperature-dependent barrier heights.