Title :
Cascode connected AlGaN/GaN HEMTs on SiC substrates
Author :
Green, B.M. ; Chu, K.K. ; Smart, J.A. ; Tilak, V. ; Hyungtak Kim ; Shealy, J.R. ; Eastman, L.F.
Author_Institution :
Dept. of Electr. & Comput. Eng., Cornell Univ., Ithaca, NY, USA
Abstract :
We report on the fabrication and characteristics of cascode-connected AlGaN/GaN HEMTs. The HEMTs were realized using Al/sub 0.3/Ga/sub 0.7/N/GaN heterostructures grown on 6-N semi-insulating SIC substrates. The circuit reported here employs a common source device having a gate length of 0.25 μm cascode connected to a 0.35 μm common gate device. The gate width of each device is 250 μm. The fabricated circuit exhibited a current density of 800 mA/mm and yielded an fT and fmax of 24.5 and 56 (extrapolated) GHz, respectively. Large signal measurements taken at 4 GHz produced 4 W/mm saturated output power at 36% power-added efficiency Comparisons to the performance of a 250×0.35 μm3 common source device taken from the same wafer show that the cascode configuration has 7 dB more linear gain and 3 db more compressed gain than the common source device at 4 GHz.
Keywords :
III-V semiconductors; aluminium compounds; current density; gallium compounds; microwave field effect transistors; microwave power transistors; power HEMT; silicon compounds; 0.25 micron; 0.35 micron; 24 GHz; 250 micron; 36 percent; 4 GHz; 56 GHz; AlGaN-GaN-SiC; SiC; cascode connected HEMTs; common gate device; common source device; compressed gain; current density; gate length; gate width; linear gain; power-added efficiency; saturated output power; Aluminum gallium nitride; Circuits; Current density; Fabrication; Gallium nitride; HEMTs; MODFETs; Performance gain; Power measurement; Silicon carbide;
Journal_Title :
Microwave and Guided Wave Letters, IEEE
