High-field electron transport and current saturation mechanism of open region channel in submicron split-gate AlGaN/GaN HFETs

Abstract Electron transport was studied at low and high electric fields, alongside current saturation mechanisms, within the open region channel of submicron split-gate AlGaN/GaN heterostructure field-effect transistors (SG HFETs). By calculating the low-field electron mobility, it is found that the gate voltage-dependent polarization Coulomb field (PCF) scattering played a dominant role in the various scattering mechanisms. A coupled Technology Computer Aided Design (TCAD) and Monte Carlo (MC) simulation method was adopted in the analysis of the high-field electron transport. When the gate–source voltage is −4 V and the drain–source voltage is 10 V, the momentum relaxation effect caused by PCF scattering reduces the peak electron velocity in the open region channel from 3 × 10 7 cm s −1 to 1.2 × 10 7 cm s −1 . The presence of the virtual gate effect in the TCAD leads to a decrease in electron density within the open region channel, creating a localized high-resistance region and consequently a local high electric field. In this high-field region, electrons attain their saturation drift velocity, resulting in current saturation. Combining the virtual gate effect and the velocity-field relationship obtained by MC simulation, the simulation results of the output characteristics at V GS ⩽ −4 V are in good agreement with the experimental results. This work extends the analysis of electron transport and PCF scattering theory in SG HFETs from low-field conditions to high-field conditions. The effect of the virtual gate effect on the channel current saturation in the open region is quantitatively revealed.