A novel composite barrier layer with back-to-back graded AlGaN in a GaN/AlGaN/GaN epitaxial structure for high performance n-and p-channel devices on the same platform is proposed. By adjusting the relative thicknesses of the two graded layers, we obtain a spread in the width and concentration of carriers in the 3D slabs. The best barrier amongst those studied, enhances the oncurrent ( 𝐼 !" ) by 24.4% in low voltage n-channel devices , 32.2% the p-channel devices whereas the figure of merit of the power device is higher by 3 times, in comparison to the conventional platform.

We report the influence of thickness of an undoped GaN (u-GaN) layer on current transport to a 2DHG through the metal/p++GaN contact in a GaN/AlGaN/GaN heterostructure. The current is dominated by an internal potential barrier of 0.2–0.27 eV at the p+ GaN/u-GaN, which increases with thickness from 5 to 15 nm and remains constant thereafter due to Fermi pinning by a defect at ∼0.6 eV from the top valence band. We also report a nonideality factor, n, between 6 and 12, for the combined tunneling current through the p+GaN/u-GaN to the 2DHG. Our contact resistivity of 5.3 × 10–4 Ω cm2 and hole mobility, μ, of ∼15.65 cm2/V s are the best-in-class for this metal stack on a GaN/AlGaN/GaN heterostructure, reported to date.

The influence of an underlying 2-dimensional electron gas (2DEG) on the performance of a normally off ptype metal oxide semiconductor field effect transistor (MOSFET) based on GaN/AlGaN/GaN double heterojunction is analyzed via simulations. By reducing the concentration of the 2DEG, a greater potential can be dropped across the GaN channel, resulting in enhanced electrostatic control. Therefore, to minimize the deleterious impact on the on-state performance, a composite graded back-to-back AlGaN barrier that enables a trade-off between n-channel devices and Enhancement-mode (E-mode) pchannel is investigated. In simulations, a scaled p-channel GaN device with L G = 200 nm, L SD = 600 nm achieves an I ON of 65 mA/ mm, an increase of 44.4% compared to a device with an AlGaN barrier with fixed Al mole fraction, I ON /I OFF of ∼10 12 , and |V th | of | − 1.3 V|. For the n-channel device, the back-to-back barrier overcomes the reduction of I ON induced by the p-GaN gate resulting in an I ON of 860 mA/mm, an increase of 19.7% compared with the counterpart with the conventional barrier with 0.5 V positive V th shift.