p-HEMT with tailored field
The high electron mobility in heterostructure devices stems from fact that electrons are injected into intrinsic layer of a semiconductor material and are confined into two-dimensional space of a heterostructure potential. However, non-linear distribution of the voltage along a transistor channel results in variation of depth and width of heterostructure potential. As in case of non-uniform electrical field in conventional field effect transistor, non-uniformity of this potential causes limitation of gain gm and operational frequency ft, increased level of noise and, most important, significantly impact the non-linearity of the gain. We illustrated our study with characteristics of tri-gate p-HEMT, fabricated on M/A-COM's high volume production AlGaAs/InGaAs process. The speed at which electrons traverse the channel was modified by providing the highest bias voltage on the first gate, and gradually decreasing the bias voltage on all subsequent gates. Thus tailored electrical field along the channel was the modeling and design base of new p-HEMTs. Manufactured devices carried in agreement with modeling, better saturation of current (large Early Voltage), significant linearity of the transconductance gm and better reliability.
p-hemt field effect transistor mosfet