AlGaN polarization-doped field effect transistor with compositionally graded channel from Al0.6Ga0.4N to AlN

Abstract

Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped AlxGa1-xN channel layer graded over Al compositions 0.60 ≤ x ≤ 1.0 with a maximum current density of 188 mA/mm (+10 V gate-to-source bias) and an on-resistance of 85 mΩ mm. The average mobility in the PolFET channel was estimated to be 320 cm2/V s, which exceeds that of previous AlGaN metal-semiconductor field effect transistors (MESFETs) and heterojunction field effect transistors (HFETs) of similar Al composition. The breakdown voltage was greater than 620 V, indicating an average critical electric field of >210 V/μm, which is substantially better than ∼100 V/μm that is typically achieved in GaN HFETs. These findings demonstrate that Al-rich PolFETs are attractive alternatives to MESFETs and HFETs for achieving simultaneously high channel electron density and mobility in high voltage switches.