Polarization-reduced quaternary InAlGaN/GaN HFET and MISHFET devices

摘要

The reduction of the polarization charge in a GaN-based single-heterostructure field-effect transistor (HFET) by polarization engineering is proposed as a method for achieving normally off operation. The concept minimizes the dependence of the threshold voltage on the barrier layer thickness. Therefore, thicker gate dielectrics for suppression of gate leakage currents can be applied without a shift in threshold voltage. A polarization-reduced enhancement-mode (E-mode) InAlGaN/GaN HFET is presented and demonstrates the basic working principle. Also an insulated-gate device with only minor shift in threshold voltage compared to the HFET validates the new concept and demonstrates the advantages compared to commonly applied concepts for E-mode operation.