Field-modulating Plate Research Articles

Observation of cross-sectional electric field for GaN-based field effect transistor with field-modulating plate

Cross-sectional potential distribution of a GaN-based field effect transistor with a field-modulating plate has been measured by Kelvin prove force microscopy to investigate the effect of the field-modulating plate on an electric field under high-voltage biasing conditions. The observed potential distribution clearly revealed that the introduction of the field-modulating plate is effective in relaxing the peak electric field intensity at the drain side of the gate edge. Furthermore, the authors experimentally observed that the peak of electric field splits into two positions: drain-side edges of the gate and field-modulating plate electrodes.

Performance of AlGaN/GaN heterojunction FETs for microwave power applications

AbstractThis paper describes design and performance of AlGaN/GaN heterojunction FETs for microwave power applications. A recessed‐gate FET with a field‐modulating plate (FP) was developed for high‐voltage power operation at L‐band and C‐band. The developed recessed FP‐FETs exhibited a 230‐W CW output power at 2 GHz and a 156‐W pulsed output power at 4 GHz. A T‐shaped 0.25‐μm‐gate FET was fabricated for high‐frequency power operation at Ka‐band. A 1.0‐mm‐wide FET exhibited a 5.8‐W CW output power at 30 GHz. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Study of surface-trap-induced gate depletion region of field-modulating plate GaAs–FETs

To investigate the cause of the superior RF output power performance of GaAs–FETs with a field-modulating plate, the impact of a field-modulating plate on the surface-trap-induced gate depletion region is evaluated using pulsed I–V characteristics of GaAs–FETs with and without a field-modulating plate. In conventional FETs (without a field-modulating plate), the very high density of the trapped electrons (∼10 12 cm −2), which are localized at the gate edge on the drain side, generates a surface depletion region extending deeply in the vertical direction. In FETs with a field-modulating plate, on the other hand, this detrimental phenomenon is significantly suppressed. Finally, this investigation shows that both RF saturated output power measured and that calculated using pulsed I–V characteristics are reasonably consistent.

CW 140 W recessed-gate AlGaN/GaN MISFET with field-modulating plate

The recessed-gate AlGaN/GaN metal-insulator-semiconductor (MIS) FET with a field-modulating plate (FP) has been fabricated. At a reverse bias condition, gate-leakage current is 10−9 A/mm and gate-drain breakdown voltage is over 200 V, which is four times higher than that of a conventional AlGaN/GaN MISFET without an FP. At 2 GHz, a 48 mm-wide recessed MIS-FP-FET demonstrated a CW saturated output power of 141 W (2.9 W/mm), a linear gain of 7.6 dB and a power-added efficiency of 56% with a drain bias of 40 V. A total CW output power of 141 W is the highest ever achieved for any III-V compound-semiconductor MISFETs.

Large-Signal Performance of Deep Submicrometer AlGaN/AlN/GaN HEMTs With a Field-Modulating Plate

This is the first time that the microwave performance of a 0.1-/spl mu/m gate in a silicon nitride window opening, with a field-modulating plate on an AlGaN/AlN/GaN heterojunction structure, is reported. The material structure was grown by organometallic vapor phase epitaxy on SiC substrates with an averaged channel sheet resistance of 313.5 ohms/square. Approximately 80-nm-thick plasma-enhanced chemical vapor deposition silicon nitride is used as the dielectric between gate metal extension and semiconductor surface. Transistors of a total gate width of 250 /spl mu/m and a 0.1 /spl mu/m gate footprint, with a 0.36 /spl mu/m long overhang on top of the silicon nitride, can be operated at a drain bias of 40-V high. Output power density of 9.5 W/mm, with 36% power-added efficiency in class AB regime, was demonstrated at 10 GHz in a continuous wave power measurement.

High-Power Recessed-Gate AlGaN–GaN HFET With a Field-Modulating Plate

Recessed-gate AlGaN-GaN heterojunction field-effect transistors (FETs) with a field-modulating plate (FP) have been successfully fabricated for high-voltage and high-power microwave applications. The developed recessed-gate FP-FET with a gate length of 1 /spl mu/m exhibited an increased transconductance of 200 mS/mm. A series of current collapse measurements revealed that the recessed-gate FP-FET is highly desirable for collapse-free high-voltage power operation. Equivalent circuit analysis demonstrated that the gain loss due to the additional gate feedback capacitance associated with the FP electrode is considerably compensated by increasing the drain bias voltage to more than 30 V. A 48-mm-wide recessed-gate FP-FET biased at a drain voltage of 48 V exhibited a record saturated output power of 197 W with a linear gain of 10.1 dB and a power-added efficiency of 67% at 2 GHz.

Improved Power Performance for a Recessed-Gate AlGaN–GaN Heterojunction FET With a Field-Modulating Plate

A recessed-gate AlGaN-GaN field-modulating plate (FP) field-effect transistor (FET) was successfully fabricated on an SiC substrate. By employing a recessed-gate structure on an FP FET, the transconductance was increased from 150 to 270 mS/mm, leading to an improvement in gain characteristics, and current collapse was minimized. At 2 GHz, a 48-mm-wide recessed FP FET exhibited a record output power of 230 W (4.8 W/mm) with 67% power-added efficiency and 9.5-dB linear gain with a drain bias of 53 V.

179 W recessed-gate AlGaN/GaN heterojunction FET with field-modulating plate

Microwave high-power performance has been achieved using a recessed-gate AlGaN/GaN heterojunction FET with a field-modulating plate. Making use of recessed-gate structure, the device exhibited an improved transconductance of 200 mS/mm with a maximum drain current of 900 mA/mm and a gate-drain breakdown voltage of 200 V. A 48 mm wide single-chip FET exhibited 179 W (3.7 W/mm) output power, 64% power-added efficiency, and 9.3 dB linear gain at a drain bias of 46 V. The saturated output power of 179 W is believed to be the highest ever achieved for any single-chip FETs.

96 W AlGaN/GaN heterojunction FET with field-modulating plate

An AlGaN/GaN heterojunction FET with a field-modulating plate has been successfully fabricated. A maximum drain current of 900 mA/mm was obtained with a gate–drain breakdown voltage of over 150 V. A 24 mm-wide FET exhibited 96 W (4.0 W/mm) output power, 54% power-added efficiency and 8.5 dB linear gain at a drain bias of 32 V.

A GaAs-based field-modulating plate HFET with improved WCDMA peak-output-power characteristics

A novel GaAs power FET with a field-modulating plate (FP-FET) and operated at a drain bias voltage of 24 V was developed. Regarding the power performance of an FP-FET under wideband code division multiple access (WCDMA) operation, its peak output power significantly degraded in the saturated-output-power region when its FP length was short. However, by introducing a sufficiently large FP length, it was demonstrated that the peak-power degradation can be significantly suppressed. In particular, an FP-FET amplifier fabricated with an FP length of 1.5 /spl mu/m exhibited no WCDMA peak-power degradation and delivered an output power of 120 W with a linear gain of 14.2 dB at 2.14 GHz.

10-W/mm AlGaN-GaN HFET with a field modulating plate

AlGaN-GaN heterojunction field-effect transistors (HFETs) with a field modulating plate (FP) were fabricated on an SiC substrate. The gate-drain breakdown voltage (BV/sub gd/) was significantly improved by employing an FP electrode, and the highest BV/sub gd/ of 160 V was obtained with an FP length (L/sub FP/) of 1 μm. The maximum drain current achieved was 750 mA/mm, together with negligibly small current collapse. A 1-mm-wide FP-FET (L/sub FP/=1 μm) biased at a drain voltage of 65 V demonstrated a continuous wave saturated output power of 10.3 W with a linear gain of 18.0 dB and a power-added efficiency of 47.3% at 2 GHz. To our knowledge, the power density of 10.3 W/mm is the highest ever achieved for any FET of the same gate size.

Analysis of electric field distribution in GaAs metal–semiconductor field effect transistor with a field-modulating plate

Electric field distribution in the channel of a field effect transistor (FET) with a field-modulating plate (FP) has been theoretically investigated using a two-dimensional ensemble Monte Carlo simulation. This analysis revealed that the introduction of FP is effective in canceling the influence of surface traps under forward bias conditions and in reducing the electric field intensity at the drain side of the gate edge under pinch-off bias conditions. This study also found that a partial overlap of the high-field region under the gate and that at the FP electrode is important for reducing the electric field intensity. The optimized metal–semiconductor FET with FP (FPFET) (LGF∼0.2 μm) exhibited a much lower peak electric field intensity than a conventional metal–semiconductor FET. Based on these numerically calculated results, we have proposed a design procedure to optimize the power FPFET structure with extremely high breakdown voltages while maintaining reasonable gain performance.