Very-high-performance highly strained Ga/sub 0.23/In/sub 0.77/As channel MODFETs

The authors report a transconductance of 843 mS/mm and a cutoff frequency 45.3 GHz for 1.2- mu m FETs and 33 GHz for 1.9- mu m FETs obtained by using a MODFET structure containing a highly strained Ga/sub 0.23/In/sub 0.77/As channel on InP substrate. It is important to either keep the gate recess quite shallow ( approximately 7 nm total) or control the process with a stop-etch layer for the achievement of these exceptionally high f/sub T/*L/sub g/ products. In device processing, three different gate-recess processes were used. Each is described. Results show that the combination of Ga/sub 0.23/In/sub 0.77/As and selective etch gate recess is an excellent technology for realizing fast FETs.