Kohji Matsunaga

Novel AlGaN/GaN dual-field-plate FET with high gain, increased linearity and stability

We have successfully developed a novel AlGaN/GaN FET with dual field-modulating-plates (FPs). The breakdown voltage is enhanced from 125 to 250 V by adding the second FP to the conventional FP structure. Benefiting from the first FP, no current collapse is observed simultaneously. Since the second FP effectively reduces feedback capacitance, this device provides a 3-dB higher gain along with increased linearity and stability. Under a 2.15-GHz W-CDMA modulation scheme, a dual-FP-FET with a 24-mm gate periphery achieved a state-of-the-art combination of 160-W output power and a 17.5-dB linear gain

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.

Highly efficient double-doped heterojunction FET's for battery-operated portable power applications

Microwave power performance of double-doped AlGaAs-InGaAs-AlGaAs heterojunction field-effect transistors (HJFETs) operated at a drain bias of 3 V is described. The fabricated 1.0 /spl mu/m gate-length HJFET exhibited a maximum drain current of 500 mA/mm, a transconductance of 300 mS/mm, and a gate-to-drain breakdown voltage of 10 V. Power performance for a 14 mm gate periphery device demonstrated a maximum output power of 1.7 W with a 66% power-added efficiency (PAE) at 900 MHz. When the device was tuned for a maximum PAE, it delivered a 71% PAE with an output power of 1.2 W. The results indicate that the developed HJFET has great potential for 3 V battery-operated portable power applications.<<ETX>>

Gate length scaling for Al/sub 0.2/Ga/sub 0.8/N/GaN HJFETs: two-dimensional full band Monte Carlo simulation including polarization effect

Two-dimensional self-consistent full band Monte Carlo (FBMC) simulator was developed for electron transport in wurtzite phase AlGaN/GaN heterojunction (HJ) FET. Recessed gate Al/sub 0.2/Ga/sub 0.8/N/GaN HJFET structures with an undoped cap layer were simulated, where the spontaneous and piezoelectric polarization effects were taken into account. The polarization effect was shown to not only increase the current density, but also improve the carrier confinement, and hence improve the transconductance. An off-state drain breakdown voltage (BV/sub ds/) of 300 V and a maximum linear output power (P/sub max/) of 46 W/mm were predicted for a 0.9-/spl mu/m gate device. For a 0.1-/spl mu/m gate device, 60 V BV/sub ds/, 20 W/mm P/sub max/, and 160 GHz current-gain cutoff frequency were predicted. Although there is considerable uncertainty due to lack of information on the band structure, scattering rates, and surface conditions, the present results indicate a wide margin for improvements over current performance of AlGaN/GaN HJFETs in the future. To our knowledge, this is the first report on the FBMC simulation for AlGaN/GaN HJFETs.

370-W Output Power GaN-FET Amplifier with Low Distortion for W-CDMA Base Stations

High output power and low intermodulation distortion (IMD) GaN-FET amplifiers are highly sought after for W-CDMA base stations. In order to obtain high output power, we have developed a field-modulating plate GaN-FET with a high maximum drain current and a high gate-to-drain breakdown voltage. Also, in order to suppress the memory effects that obstruct digital predistortion (DPD) linearization in W-CDMA power amplifiers, we have newly developed the bias network, in which frequency-dependent impedance at the base band of multi-carrier W-CDMA signals is reduced. As a result, the GaN-FET amplifier developed for W-CDMA base stations achieves a record 370-W W-CDMA peak output power, and a low DPD linearized IMD of less than -50 dBc at the highest W-CDMA average output power of over 60 W, resulting in a significant improvement of DPD linearization not only in IM3 but also in IMS and IM7

A CW 4 watt Ka-band power amplifier utilizing MMIC multi-chip technology

This paper describes a 28 GHz power amplifier with 4.5 W output power under CW operation. The amplifier utilizes four fully-matched MMICs, in which 0.35 /spl mu/m-long gate GaAs-based heterojunction FETs are employed. The developed power amplifier also provides the highest CW output power of 3 W over the bandwidth of 2 GHz at Ka-band.

A 12-GHz, 12-W HJFET amplifier with 48% peak power-added efficiency

This letter describes a Ku-band power amplifier fabricated with a one-chip 0.45 μm×16.8 mm GaAs-based heterojunction FET (HJFET), in which a 40.9 dBm (12.3 W) output power with 48% power-added efficiency (PAE) and 10.1 dB linear gain was achieved at 12 GHz. To our knowledge, this is the highest PAE, gain and output power combination achieved by a single FET power amplifier at this frequency.

Field-modulating plate (FP) InGaP MESFET with high breakdown voltage and low distortion

This paper describes a successfully developed field-modulating plate (FP) InGaP MESFET with an extremely high breakdown voltage of 100 V. The FP-FET, consisting of a 2.62 mm gate width, delivered an output power of 4.3 W and an output power density of 1.6 W/mm at 1.95 GHz operated at a drain bias (Vd) of 55 V. A low 3rd-order intermodulation distortion (IM3) of -31 dBc was also achieved at 8 dB back-off from saturation power. These results show the developed FET is suited for applications in the next generation cellular base station.

100 W L-band GaAs power FP-HFET operated at 30 V

This paper reports an L-band power AlGaAs/GaAs heterostructure FET with a field-modulating plate (FP-HFET), which accomplished 100 W output power with a high power density of 1.16 W/mm at a drain bias voltage of 30 V. The developed FP-HFET is promising for achieving improved performance and reduced size of digital cellular base station systems.

A low-distortion 230 W GaAs power FP-HFET operated at 22 V for cellular base station

This paper describes a successfully developed L-band depletion-mode GaAs-based heterostructure FET (HFET) with a field-modulating plate (FP) for cellular base station applications. The FP-HFET power amplifier, consisting of four 86.4 mm gate-width chips, delivered a 53.6 dBm (230 W) output power at 2.1 GHz with 11 dB linear gain and 42% PAE operated at a drain bias of 22 V. A low adjacent channel leakage power ratio (ACPR) of -35 dBc with 25% PAE was obtained at an output power of 46 dBm, indicating superior linearity characteristics under elevated drain bias conditions. The device also exhibited a record saturated power density of 0.67 W/mm.