Epitaxial high-K barrier AlBN/GaN HEMTs

We report a polarization-induced 2D electron gas (2DEG) at an epitaxial AlBN/GaN heterojunction grown on a SiC substrate. Using this 2DEG in a long conducting channel, we realize ultra-thin barrier AlBN/GaN high electron mobility transistors that exhibit current densities 0.25 A/mm, clean current saturation, a low pinch-off voltage of −0.43 V, and a peak transconductance of ∼0.14 S/mm. Transistor performance in this preliminary realization is limited by the contact resistance. Capacitance–voltage measurements reveal that introducing ∼7% B in the epitaxial AlBN barrier on GaN boosts the relative dielectric constant of AlBN to ɛrAlBN∼16, higher than the AlN dielectric constant of ɛrAlN∼9. Epitaxial high-K barrier AlBN/GaN HEMTs can thus extend performance beyond the capabilities of current GaN transistors.