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The emerging Al-rich AlGaN-channel Al x Ga1−x N/Al y Ga1−y N high-electron-mobility transistors (HEMTs) with 0.7 ≤ y < x ≤ 1.0 have the potential to greatly exceed the power handling capabilities of today's GaN HEMTs, possibly by five times. This projection is based on the expected 4× enhancement of the critical electric field, the 2× enhancement of sheet carrier density, and the parity of the electron saturation velocity for Al-rich AlGaN-channel HEMTs relative to GaN-channel HEMTs. In this paper, the expected increased RF power density in Al-rich AlGaN-channel HEMTs is calculated by theoretical analysis and computer simulations, based on existing data on long-channel AlGaN devices. It is shown that a saturated power density of 18 W mm−1, a power-added efficiency of 55% and an output third-order intercept point over 40 dB can be achieved for this technology. The method for large-signal RF performance estimation presented in this paper is generic and can be applied to other novel high-power device technologies at the early stages of development.

Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped Al x Ga1− x N channel layer graded over Al compositions 0.70 ≤ x ≤ 0.85 and ohmic contact formation to the Al0.85Ga0.15N surface. Current density of 24 mA/mm was attained for a modest threshold voltage of −3.95 V owing to the high sheet charge concentration (n s) of 5.4 × 1012 cm−2 and average electron mobility (μ) of 210 cm2 V−1 s−1 for the channel region along with ohmic contacts with a specific contact resistivity of 1.1 mΩ cm2 and a large Schottky barrier height of 3.0 eV for the metal–semiconductor gate. The combination of ultra-wide band gap energy, high μ, and high n s, linear ohmic contacts, and large Schottky barrier for AlGaN PolFETs makes them attractive for both high voltage switches and high power rf devices.