Record 1 W output power from a single N-Polar GaN MISHEMT at 94 GHz

Emre Akso, Christopher Clymore, Wenjian Liu, Henry Collins, Brian Romanczyk, Weiyi Li, Nirupam Hatui, Christian Wurm, Stacia Keller, Matthew Guidry, Umesh K. Mishra

Abstract: Combining excellent dispersion control with large breakdown voltage, deep recess N-polar GaN HEMT technology has demonstrated record high power densities [1] and efficiencies [2]–[3] from 2-finger devices with <tex>$50-75\ \mu \mathrm{m}$</tex> gate peripheries at W-band. Employment of this technology in MMICs, however, will benefit from larger periphery multi-finger devices to maximize the power per unit cell and thus reduce or even possibly eliminate power combining for many applications. This will in turn increase the system efficiency by reducing the combining losses and enable more compact phased-arrays at mm-wave frequencies. Recently, a <tex>$4\times 25\ \mu \mathrm{m}$</tex> multi-finger N-Polar GaN HEMT with record 712 mW output power was reported [4]. Increasing the gate periphery further (<tex>$&gt; 100\ \mu \mathrm{m}$</tex>) to maximize the power per cell requires a smaller load line resistance and larger capacitance compensation for optimal matching, thereby pushing the optimum load reflection coefficient magnitude to the values not obtainable by passive load pull, as shown in Fig 1. In this paper, we demonstrate an optimally load line matched <tex>$4\times 37.5\ \mu \mathrm{m}$</tex> N-Polar GaN HEMT with 1 W (999.1 mW) output power at 20 V, measured with our new vector active load pull capability [5] at 94 GHz. To the best knowledge of the authors, this power is the highest reported output power from a single transistor to date at W-band.