Stability in Fluorine-Treated Al-Rich High Electron Mobility Transistors with 85% Al-Barrier Composition.

Combined with recess etching, Al-rich III-N high electron mobility transistors (HEMTs) can be treated with a reactive ion etch plasma to implant F- ions into the HEMT's near surface region for a positive threshold voltage $(V_{TH})$ shift to achieve enhancement-mode (e-mode) operation. These HEMTs, along with depletion-mode (d-mode) controls that lack fluorine treatment, were evaluated for F- ion stability using step-stress and fixed-bias stress experiments. Step-stress experiments identified parametric shifts as a function of the drain-voltage $(V_{DS})$ stress prior to catastrophic failure that occurred at ${\it V_{DS}}$ ranging between 70–75 V. Fixed bias stressing at $V_{DS}=50\mathrm{V}$ was conducted at $190\ ^{\circ}\mathrm{C}$ Both e- and d- mode HEMTs exhibited a negative $V_{TH}$ shift of $0.6-1.0 \mathrm{V}$ during early time stressing at 190°C, with minor on-resistance effects, but both HEMT types were thereafter stable up to 4 hours. The early time changes are common to both e-mode and d-mode HEMTs and the F-induced ${\it V_{TH}}$ delta between e- and d-mode HEMTs remains intact within the bias-temperature stressing conditions of this work.