Katsumi Yamanoguchi

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

High performance 60-GHz coplanar MMIC LNA using InP heterojunction FETs with AlAs/InAs superlattice layer

We describe a 60-GHz coplanar MMIC low-noise amplifier (LNA) using 0.1 /spl mu/m-gate-length InP heterojunction FETs (HJFETs). An optimum gate width of 80 /spl mu/m was determined for the first stage FET by using a small signal model including accurate scaling of the gate resistance. On-wafer noise measurements demonstrated a noise figure of 2.2 dB and a gain of 22.8 dB at 60 GHz.

C-band single-chip GaN-FET power amplifiers with 60-W output power

A C-band high power amplifier was successfully developed with a single-chip GaN-based FET. At 4.0GHz, the fabricated 24-mm wide FET delivers 62 W and 156W under CW and pulsed operating conditions, respectively with a universal test fixture. The internal matching circuit was designed to be set up in a half-size package as compared to that for GaAs-based comparable- power-level amplifiers. The developed GaN-FET amplifier with 24-mm gate periphery delivers a 61W output power with 10.2dB linear gain and 42% power-added efficiency under CW operating conditions. To the best of our knowledge, this is the highest CW output power achieved from a single-chip FET power amplifier at C-band.

A 76 GHz GaN-on-silicon power amplifier for automotive radar systems

This paper describes the first demonstration of a 76 GHz gallium nitride (GaN) power amplifier (PA) on a silicon substrate. The PA microwave monolithic IC (MMIC) was fabricated by using AlGaN/GaN FET with a maximum oscillation frequency of 160GHz and a breakdown voltage of over 50 V. For reducing transmission loss, we used a CPW line on the silicon substrate with low transmission loss of 0.5 dB/mm at 76 GHz. For precise design of the PA, a large signal model of the FET was developed. The developed CPW 3-stage PA exhibited an output of over 12 dBm with over 5 dB gain at 75–81 GHz.

Theoretical and Experimental Study of Inverse Piezoelectric Effect in AlGaN/GaN Field-Plated Heterostructure Field-Effect Transistors

This paper reports the theoretical and experimental study of the inverse piezoelectric effect in AlGaN/GaN heterostructure field-effect transistors (HFETs) with field plate (FP) electrodes. The theoretical analysis based on the 2-D Monte Carlo simulation predicted that introducing the FP structure drastically decreases the elastic energy due to the inverse piezoelectric effect. The extension of gate-connected or source-connected FP electrode and thinning a SiN film under FP were found effective to improve the critical voltage (Vcrit) for degradation under reverse bias stress. Also, calculated trends of Vcrit as a function of FP lengths and a SiN film thickness were qualitatively verified by step-stress measurements of field-plated HFETs fabricated on Si substrates. These results clearly indicate that the optimization of the FP structure minimizes degradation associated with the inverse piezoelectric effect in AlGaN/GaN HFETs.

CW 20-W AlGaN/GaN FET Power Amplifier for Quasi-Millimeter Wave Applications

This paper describes an AlGaN/GaN FET power amplifier module delivering a continuous wave (CW) output power of more than 20 W at 26 GHz. To achieve high breakdown characteristics with reduced current collapse and high gain, we have developed a 0.2 µm-long recessed-gate AlGaN/GaN FET with a field-modulating plate (FP), achieving high operation voltage of 25 V even at quasi-millimeter wave frequencies. A single-ended AlGaN/GaN FP-FET amplifier module for quasi- millimeter wave frequency has been fabricated for the first time. The amplifier module developed using a 6.3-mm-wide single chip recessed-gate AlGaN/GaN FP-FET exhibited an output power of 20.7 W, a linear gain of 5.4 dB and a power-aided efficiency of 21.3% at 26 GHz. This is the highest output power in solid state power amplifiers at over 20 GHz.

Enhancement-mode GaN-on-Si MOS-FET using Au-free Si process and its operation in PFC system with high-efficiency

We have developed an enhancement-mode GaN-on-Si MOS-FET with a thin GaN channel (40nm) on a thick AlGaN back barrier layer (1um), using Au-free 150-mm Si process. The developed device showed a threshold voltage Vt of 1.1 V, an on-resistance Ron of 5.4 mΩcm2 and a breakdown voltage BV of 730 V. The developed E-mode GaN MOS-FETs demonstrated the potential for compact and efficient power electronics. A Power Factor Correction (PFC) circuit using the packaged GaN device (20A, 650V) operated with high efficiency of > 94 % at Pout=300 W, Vout=390 V and fSW=300 kHz.

V-band MMIC LNA using superlattice-inserted InP heterojunction FETs

This paper presents a V-band MMIC low-noise amplifier (LNA) using InP-based heterojunction FETs (HJFETs). While the HJFET utilizes an AlAs/InAs superlattice as well as non-alloyed ohmic contacts for improved reliability, we show that with appropriate epitaxial layer design these device structures do not lead to increase in the source resistance. The three-stage coplanar waveguide circuit design demonstrated a state-of-the-art noise figure of 2.0 dB with 22.1 dB gain at 60 GHz.

A low distortion 38 GHz-band high power MMIC amplifier

The growth of the point to point and the point to multipoint radio markets has produced a demand for high power, low distortion and cost effective amplifier at quasi-millimeter-wave. This paper describes a GaAs-based monolithic microwave integrated circuit (MMIC) amplifier having watt-level power performance, excellent third order intermodulation distortion (IMD3) characteristic at 38 GHz-band for various communication system applications. We have developed GaAs-based double-doped heterojunction FETs (HJFET) for quasi-millimeter-wave MMIC amplifier, using highly-uniform 0.2 /spl mu/m WSi-gate process on 5-inch GaAs wafer.

Robust 0.13-μm Gate HJFET with Low Fringing Capacitance

l. Introduction The millimeter-wave bands are atffacting considerable attention, being suitable for focused-beam radars. GaAs-based heterojunction FETs (HJFETs) are widely used in millimeter-wave Vand W-bands. T:shaped gates with a length of around 0.lpm [1] are generally adopted to achieve a high-gain in millimeter-wave bands, although such an ultra-short gate is liable to peel off the semiconductor surface. To overcome this problem, gates are commonly embedded in a dielectric layer l2l.However, the dielectric layer increases the parasitic gate capacitance (for Cgs and Cgd) and adversely affects the high-frequency gain [3]. To meet the needs for both a high yield and high-frequency gain at the same time, we have been investigating a new gate sffucture, in which segments of the gate are supported by an embedding SiO2 film, and the remainder is unsupported. This stmcture can be built using the fabrication process explained below, where the SiO2 film around the embedded gates is partially removed along the fingers in a striped pattern.