Investigation of step graded channel heterostructure field effect transistor with high gate voltage swing

In order to enhance the electron mobility we use step graded channel structure in the heterostructure field effect transistor to reduce Coulomb scattering. The electrons are far away from the AlGaAs/InGaAs interface. We fabricated successfully and obtained high drain current density and large gate voltage swing. For a 1.2/spl times/100 /spl mu/m/sup 2/ gate dimension, the maximum saturation drain current density is 373 mA/mm and the maximum extrinsic transconductance is 148 mS/mm along with the gate voltage swing of 1.9V. Additionally, we use four period AlGaAs/GaAs buffer layer so that the variations of threshold voltages are insensitive to temperature.