Wide Bandgap MMIC Technology

Doctoral thesis, 2008

Wide bandgap technology for microwave electronics has been an intense area of research during the last decade. With reas of application ranging from base station amplifiers to radar transceivers, this technology has the resources to be the basis for the next generation of high power microwave electronics. The unique properties of these transistors have enabled the fabrication of high power, broadband, high efficiency and linear microwave electronics better than that possible in either Si or GaAs technology. This work has focused on MMIC (microwave monolithic integrated circuit) technology through development of a process and design technology, and evaluation of typical components for transceiver applications. The MMIC technology is based on SiC MESFETs and AlGaN/GaN HEMTs, and is designed for high power operation with high voltage MIM capacitors (breakdown voltage >200V), low resistance spiral inductors, TaN thin film resistors, and through substrate via-holes. The SiC MESFETs show power densities of 8W/mm at 3GHz, fT /fmax figures of 8/30GHz and a DC transconductance, gm, of 25mS/mm. The AlGaN/GaN HEMTs show power densities of 5W/mm at 10GHz, NFmin of 1.2dB at 10GHz, fT /fmax figures of 23/52GHz and a gm of 300mS/mm. Transceiver circuitry for 3 and 10GHz operation is demonstrated with power amplifiers delivering more than 5W of output power at 3GHz at power added efficiencies (PAE) up to 32%, and 5W at 10GHz at a PAE just below 10%. A 2-18GHz transmit/receive switch with an insertion loss of less than 2dB up to 10GHz is demonstrated for implementation in TDD (time division duplex) systems. Robust small signal amplifiers able to withstand overdrive levels of 5W are demonstrated, as well as highly linear mixers at 3 and 10GHz. An 11.6GHz mixer with an integrated RF preamplifier illustrates the possibility to realize multifunction MMICs in AlGaN/GaN technology, and the capability to use SiC MMIC for power control is demonstrated through a DC/DC converter demonstrating an 80% conversion efficiency.