On the optimization of GaN HEMT layout for highly rugged low-noise amplifier design

Abstract

GaN low-noise amplifiers need to provide low noise figure, but are also often expected to be highly rugged. This paper addresses the question, how HEMT devices within a certain technology can be optimized only by changing basic geometrical properties. While epitaxial layer structure and gate length usually are not accessible, the circuit designer might be able to choose parameters as gate finger width and gate-source spacing. In this analysis, GaN HEMT samples were fabricated, measured and modeled. The layout of the devices was varied in order to study possibilities to improve noise figure. It is shown that significant improvements in noise performance are to be expected by optimizing gate finger width, while the slight improvement in terms of noise figure resulting from a reduction in gate-source spacing compromises gate breakdown and should be avoided. This work provides the designer of low-noise amplifier MMICs with a qualitative analysis and quantitative examples of a state-of-the art GaN HEMT process how to optimize the layout of the HEMT for low-noise and highly rugged LNA design.