Enhancement- and depletion-mode AlGaN/GaN HEMTs on 3C-SiC(111)/Si(111) pseudosubstrates

Abstract

The realization of depletion-mode planar and both enhancement-and depletion-mode tri-gate high electron mobility transistors (HEMTs) based on Al 0.2 Ga 0.8 N/AlN/GaN heterostructures grown on silicon substrates using an ultrathin 3C-SiC transition layer is presented. This substrate configuration simplifies heterostructure growth compared to SiC and thick 3C-SiC substrates. The threshold voltage of the tri-gate devices strongly depends on the AlGaN/GaN body (fin) width. A transition from depletion-mode to enhancement-mode operation occurred at 110 nm body width for tri-gate devices without Si 3 N 4 passivation, and is expected to occur at 75 nm for devices with Si 3 N 4 passivation. Threshold voltages of À0.25/ 0.35 V were achieved at fin widths of 82/100 nm with/without Si 3 N 4 passivation, respectively, for the tri-gate HEMTs in comparison to À3.5 V for the planar HEMTs. Cutoff frequencies f T of 45 GHz and maximum frequencies of oscillation f max of 50 GHz have been measured for our best 100-nm tri-gate enhancement-mode HEMTs, while depletionmode planar HEMTs with the same gate length showed 110 GHz for both f T and f max . This demonstrates the applicability of the developed substrate configuration for high-performance device applications.

Selective GaN sublimation and local area regrowth for co-integration of enhancement mode and depletion mode Al(Ga)N/GaN high electron mobility transistors

“…A second way consists of the partial or total etching of the barrier to achieve a gate recess [10][11][12][13][14]. Tri-gate topologies have also been developed to enhance the carrier confinement and V th shift [15]. Yet, another way to shift V th is to introduce additional layers such as p-doped GaN or InGaN on top of the barrier layer [16][17][18][19][20].…”