Plasmon-controlled optimum gate bias for GaN heterostructure field-effect transistors

Electron density-dependent dc, rf and power characteristics are investigated for nearly lattice-matched InAlN/AlN/GaN heterostructure field-effect transistors (HFETs). The best performance in respect to transconductance and cutoff frequency is demonstrated at the optimal gate bias of −8 V for the devices with electron sheet density of 3 × 10 13 cm −2 (measured on Hall bars of as-grown heterostructures). The results are in fair agreement with the universal bias‐density relation controlled by the plasmon-assisted ultrafast decay of nonequilibrium optical phonons launched by hot electrons.