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In GaN Schottky barrier diodes (SBD), there is a trade-off between the turn-on voltage and the leakage current. In this study, recess-free 4 nm-thin-barrier AlGaN/GaN SBDs with minimal leakage current as well as excellent turn-on voltage homogeneity are developed, which enable better electrical control to pinch off the 2DEG channel under the anode region and avoids trap introduced in the barrier etching process. In detail, the effect of reverse stress on the SBD performance is initially explored by using differential conductance, and then, the anode-to-cathode distances and temperatures dependence of SBDs output characteristics are systematically studied. The fabricated thin-barrier GaN SBDs show a turn-on voltage of ∼0.75 V and a low level leakage current of 9.66 × 10−10 (1.91 × 10−8) A/mm at 300 (423) K, which is among the lowest reported values at the comparable reverse bias voltage and temperature. Moreover, structure parameters of the thin-barrier AlGaN/GaN SBD are systematically modeled and optimized by the TCAD simulations, including anode metal work function, Al mole fraction, the anode-to-cathode distance, and slanted anode angle. The introduction of slanted anode is found to have significant effect on the improvement of reverse breakdown voltage and leakage current characteristics. [ABSTRACT FROM AUTHOR]

In this paper, an observation of drain current instability on p-GaN gate AlGaN/GaN HEMTs is reported. Contrary to the Schottky gate AlGaN/GaN HEMTs, which show stable and consistent Id – Vd curves under different pulsed conditions, the Id – Vd curves for p-GaN gate AlGaN/GaN HEMTs show a dispersion in the saturation region under the same pulse conditions, which cannot be explained by the trapping of electrons in the material. A model considering the trapping of holes in the p-GaN gate under different gate and drain biases is proposed to explain this new phenomenon. [ABSTRACT FROM AUTHOR]

During off-state, the influence of surface-trapped electron charges induced by high-field stress near the gate electrode of AlGaN/GaN power high-electron mobility transistor devices causes a reduction in two-dimensional electron gas (2DEG) carrier density at the heterointerface. In a pulse turn-on operation, the weakened 2DEG channel results in a higher on-state conduction resistance during the transient, known as the current collapse phenomenon. The phenomenon increases the switching loss by a higher on-state resistance and prolonged turn-on transition time, thus limits the device operating frequency range. In this paper, such a phenomenon is modeled, analyzed by Sentaurus TCAD simulation, and verified by the laboratory measurement data, with the emphasis on the influence of field plates toward the current collapse. The spatial distributions of trapped electrons and excess free electrons along the AlGaN surface are modeled and analyzed to arrive at the quantitative relationships among the trapped electron density, on-resistance increase, and the electric field distribution which provide a reliable criterion for current collapse reduction. It was found that, with a proper field plate design, it is possible to achieve an improvement on transient on-state resistance and the current recovery time. [ABSTRACT FROM AUTHOR]

This paper reports extensive modelling and analysis of the temperature dependence on the device characteristics of the AlGaN/GaN high electron mobility transistors (HEMTs). A physics-based model is proposed in this study in order to correctly predict the gate flat-band Schottky barrier height, energy band Fermi-level (EC–EF) at the AlGaN/GaN interface, two-dimensional electron gas sheet density, gate threshold and (ID–VG) at sub-threshold voltages, and drain current–voltage (ID–VD) characteristics under various high-temperature conditions. The analytical results are then verified by comparing with the laboratory measurement as well as the numerical results obtained from the Sentaurus TCAD simulation. The proposed model is found to be useful for power electronic device designers on the prediction of the AlGaN/GaN HEMT device performance under high-temperature operation. [ABSTRACT FROM AUTHOR]

In this letter, the approach of partial AlGaN recess and multiple layers of fluorinated Al2O3 gate dielectric is utilized to achieve highest reported positive gate threshold voltage ( $V_{{{\textrm {TH}}}}$ ) without severe reduction on 2-D electron gas carrier mobility in AlGaN/GaN HEMTs. Guided by the design and verification through analytical model, proper fluorine ions incorporation is made through fabrication. The approach resulted in a high $V_{{{\textrm {TH}}}}$ of +6.5 V and competitive drain saturation current ( $I_{{{\textrm {DMAX}}}}$ ) of 340 mA/mm. Furthermore, low gate leakage current and high breakdown voltage of 1140 V were also demonstrated. [ABSTRACT FROM AUTHOR]

In this letter, partially recessed gate structures in conjunction with negative trap charges by F^- plasma treatments both at AlGaN barrier and on gate dielectric surface are employed to realize the normally-OFF operation for AlGaN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors in Au-free scheme. A partial gate recessed trench is designed to effectively reduce the 2-D electron gas (2DEG) density and achieve positive threshold voltage (Vth) without severe degradation in 2-DEG channel mobility. Furthermore, the fixed trap charges are innovatively placed at the gate AlGaN and Si3N4 layers by a two-stage F^- plasma treatment to further increase the Vth , without mobility degradation. A high Vth of 1.9 V and a drain current \sim200~mA/mm are achieved in the fabricated device, which also has a lower leakage current and the higher breakdown voltage of 580 V. [ABSTRACT FROM AUTHOR]

A novel structure scheme by transposing the gate channel orientation from a long horizontal one to a short vertical one is proposed and verified by technology computer-aided design (TCAD) simulations to achieve GaN-based normally-off high electron mobility transistors (HEMTs) with reduced on-resistance and improved threshold voltage. The proposed devices exhibit high threshold voltage of 3.1 V, high peak transconductance of 213 mS, and much lower on-resistance of 0.53 mΩ·cm2 while displaying better off-state characteristics owing to more uniform electric field distribution around the recessed gate edge in comparison to the conventional lateral HEMTs. The proposed scheme provides a new technical approach to realize high-performance normally-off HEMTs. [ABSTRACT FROM AUTHOR]