A novel fabrication process and analytical model for Pt/GaAs Schottky barrier mixer diodes

Abstract

A new fabrication process for small-area honeycomb structured GaAs Schottky barrier diodes is described. This fabrication process is based on the anodic pulse etching technique of GaAs in combination with an electrolytic in situ Pt deposition. The presented diodes exhibit nearly ideal I/V and noise characteristics. An analytical model has been developed to self-consistently model the fabricated near-ideal Schottky barrier diodes. The analytical model includes the effects of a current dependent recombination velocity, an accurate derivation of the spreading resistance for epitaxial diodes, a n-n + junction voltage dependent on the diode current and a bias dependent barrier height. A closed-form expression for the recombination current in the depletion region is given. This model, compared to the simple thermionic model is able to determine technology dependent parameters such as the bias dependent series resistance and junction capacitance as well as the current dependent noise temperature. These are the most important diode parameters which define the diode mixing performance. Although the simple thermionic model also fits the measured data very well, it is shown that the physical parameters of the Schottky diodes, determined by this approach, are inaccurate. The novel analytical model gives new insight into the physical understanding of forward biased epitaxial Schottky diodes with small junction areas.