Components for AlGaN/GaN Power Amplifiers

Abstract

Ohmic contacts and Schottky contacts were made on an undoped AlGaN/GaN FET structure. Despite the high Al content (33%), we were still able to obtain a contact resistance of 0.3 ωmm. Pulsed measurements showed the large effect of self-heating even for circular contacts with a radius of 50 μm. The behavior ofthe Ni/Au Schottky contacts is according to the charge control model; the reverse current and capacitanceonly scale with the area of the diode. Tests with polygon type diodes showed no dependence of the reverse current on the number of polygon corners. The reverse current decreased when the devices were aged at 400°C for 30 hrs. Coplanar Waveguide discontinuities were realized on AlN substrates. A scalable lumped element model was derived from measurements for T-junctions, transmission lines, bends and crosses.