Slant Field Plates Research Articles

Demonstration of 16 THz V Johnson's figure-of-merit and 36 THz V fmax·VBK in ultrathin barrier AlGaN/GaN HEMTs with slant-field-plate T-gates

In this work, ultrathin barrier (∼6 nm) AlGaN/GaN high-electron-mobility transistors (HEMTs) with in situ SiN gate dielectric and slant-field plate (SFP) T-gates were fabricated and analyzed. Since the proposed scheme of gate dielectric and SFP effectively suppresses the gate leakage and alleviates the peak electric field (E-field) around gate region, the maximum breakdown voltage (VBK) was improved to 92 V, which is 54 V higher than that of the conventional device. The fabricated ultrathin AlGaN/GaN HEMT with 60-nm SFP-T-gate exhibited the peak fT of 177 GHz and peak fmax of 393 GHz, yielding high figure-of-merits of fT · VBK = 16 THz V and fmax·VBK = 36 THz V. Moreover, load-pull measurements at 30 GHz reveal that these devices deliver output power density (Pout) of 4.6 W/mm at Vds = 20 V and high power-added efficiency up to 52.5% at Vds = 10 V. Essentially, the experimental results indicate that the employment of SFP and in situ SiN gate dielectric is an attractive approach to balance the breakdown and speed for millimeter wave devices.

Improving Off-State Breakdown Voltage of a Double-Channel AlGaN/GaN HEMT with Air-Bridge Field Plate and Slant Field Plate

The off-state breakdown voltage of a double-channel AlGaN/GaN HEMT is improved by employing an air-bridge field plate (AFP) and a slant field plate at the gate electrode. It has been observed that using the AFP only can reduce the peak electric field under the gate edge to a certain extent, and a slant field plate can be added to obtain an even better result. The breakdown voltage is increased from 19 V of the initial structure to 200 V of the optimized structure.

Effect of surface passivation on the electrical performance of AlGaN/GaN high‐electron‐mobility transistors with slant field plates fabricated using deep‐UV lithography

AlGaN/GaN high‐electron‐mobility transistors (HEMTs) have been extensively applied for high power applications at high frequencies. To further improve the device performance, field plates and passivation layers are commonly integrated with the device technology. This paper is to investigate the effects of surface passivation thickness on the electrical performance of AlGaN/GaN HEMTs with slant field plates fabricated using deep‐UV technology. As a benchmark, the device without nitride passivation exhibited a peak transconductance of 214 mS/mm and a breakdown voltage of 122 V with an output power of 5.0 W/mm at 8 GHz. For the passivated devices, it is observed that the existence of the silicon nitride passivation layer helps to improve the DC characteristics of the devices in terms of the lower drain current collapse, higher maximum DC transconductance, and higher maximum drain current. RF wise, the devices with passivation suffer from lower fT and fMAX due to the increase in the gate capacitances. However, an improvement of RF output power was observed for devices with passivation layer thickness up to 300 nm.

Achievement of balanced high frequency and high breakdown by InGaAs-based high-electron-mobility transistors with slant field plates

InGaAs-based high-electron-mobility transistors (HEMTs) with SiCN-based multistep slant field plates (FPs) and two-step recess (TSR) gates are fabricated and characterized. The slant FPs, which were originally developed for GaN-HEMTs, are integrated with InGaAs-HEMTs to increase the breakdown voltage (BV). The BVs of InGaAs-HEMTs increase by a factor of 1.5–2. However, FPs have a negative effect on the current gain cutoff frequency (fT). Consequently, BV and fT have a trade-off relationship. The combination of slant FPs and TSR gates enables the achievement of a balanced BV and fT of 8.0 V and 106 GHz, respectively, in 130-nm-gate-length InGaAs-HEMTs.

A new process approach for slant field plates in GaN-based high-electron-mobility transistors

A new process approach to realize a slant field plate — a field plate (FP) gradually separated from the semiconductor surface from the gate edge toward the drain — is reported. A multistep SiCN dielectric film is used to make a sloped sidewall in the dielectric film consisting of a slant FP. The sidewall shape is controlled by the number of steps in SiCN. AlGaN/GaN high-electron-mobility transistors (HEMTs) with slant and conventional FPs are prepared using this technique. The advantage of slant FPs over conventional FPs is experimentally confirmed as a result of reduced current collapse, higher current gain cutoff frequency, and higher off-state breakdown voltage.

Improved breakdown voltage and RF characteristics in AlGaN/GaN high-electron-mobility transistors achieved by slant field plates

We experimentally demonstrate the efficacy of using slant field plates (field plates with the plate-to-channel gap gradually increasing away from the gate edge) on the breakdown voltage. We develop a new fabrication process using a multi-step SiCN film such that both slant and conventional field plates are fabricated simultaneously. Consequently, we fabricate 230-nm-gate AlGaN/GaN HEMTs with several types of field plates. The slant field plate increases the breakdown voltage by 66% more than that of the conventional field plate. The advantages of using slant field plates to increase the breakdown voltage are experimentally confirmed for the first time.

Current collapse suppression in AlGaN/GaN HEMTs by means of slant field plates fabricated by multi-layer SiCN

We report a new fabrication process to realize a slant field plate – a field plate in which the plate-to-channel distance gradually increases with the distance from the gate edge – using a multi-layer SiCN film. AlGaN/GaN HEMTs with several types of field plates are fabricated by this technique. The current collapse in the pulsed measurements is suppressed by the slant field plates more effectively than the conventional parallel-plate field plates as a result of the reduced electric field at the gate edge.

N-Polar GaN MIS-HEMTs With a 12.1-W/mm Continuous-Wave Output Power Density at 4 GHz on Sapphire Substrate

This letter presents a high-performance N-polar AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor grown by metal-organic chemical vapor deposition on sapphire substrate. The devices were passivated with Si <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> N <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> deposited by plasma-enhanced CVD and consisted of a gate structure recessed through the Si <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> N <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> passivation, with integrated slant field plates, to prevent dc to RF dispersion and improve the breakdown voltage. Devices with a drawn gate length of 0.7 μm and a gate drain spacing of 0.8 μm showed a breakdown voltage of 170 V, corresponding to a three-terminal leakage current of 1 mA/mm. Due to the high breakdown voltage of the devices, continuous-wave RF power measurements at 4 GHz could be measured at a drain bias of 50 V, yielding an output power density of 12.1 W/mm. To the best of our knowledge, this is the highest power density reported so far for an N-polar device and also matches the highest power density reported for a Ga-polar HEMT on the sapphire substrate.

Deep-Submicrometer AlGaN/GaN HEMTs With Slant Field Plates

Deep-submicrometer AlGaN/GaN HEMTs with integrated slant field plates have been fabricated. Simulation showed this technology had the ability to minimize both the dc-RF dispersion and parasitic capacitance. Prototype device results demonstrated an excellent millimeter-wave power density of 4.9 W/mm with a power-added efficiency of 45% at 30 GHz at a drain bias of 30 V.

Effect of Al Composition and Gate Recess on Power Performance of AlGaN/GaN High-Electron Mobility Transistors

AlGaN/GaN high-electron mobility transistors with different Al compositions and barrier thicknesses were compared. The samples with higher Al composition and similar 2D electron gas density showed higher gate leakage, utilizing a slant field plate gate process. By applying a gate recess etch and a slant field plate gate process, gate leakage was improved to a similar level for all the devices, and the power density and PAE were much improved.