Yoshitaka Niida

Collapse-free high power InAlGaN/GaN-HEMT with 3 W/mm at 96 GHz

In this work, we demonstrated an excellent output power (Pout) density of 3.0 W/mm at 96 GHz using a novel collapse-free InAlGaN/GaN-HEMT with an 80-nm gate for a millimeter-wave amplifier. The developed devices showed basic reliability for commercial products. To eliminate the current collapse, a unique double-layer silicon nitride (SiN) passivation film that has oxidation resistance was adopted. We proved the potential of InAlGaN/GaN-HEMT using our unique device technology experimentally and analytically.

3.6 W/mm high power density W-band InAlGaN/GaN HEMT MMIC power amplifier

We demonstrated a W-band high-power-density MMIC power amplifier with 80 nm InAlGaN/GaN HEMTs. The MMIC consists of two-stage cascade units, each of which has two transistors with the same gate periphery for a high gain and low-loss matching circuit. The MMIC achieved a maximum output power of 1.15 W and maximum PAE of 12.3 % at 86 GHz under CW operation. Its power density reached 3.6 W/mm, representing the highest performance of the W-band GaN HEMT MMIC power amplifier.

Millimeter-Wave GaN HEMTs With Cavity-Gate Structure Using MSQ-Based Inter-Layer Dielectric

We have fabricated millimeter-wave gallium nitride high electron mobility transistors (GaN HEMTs) using methyl silsesquioxane (MSQ)-based inter-layer dielectric to suppress current collapse by enhancing the moisture resistance, and removed MSQ around the gate electrode for reducing parasitic capacitance. We clarified that the moisture resistance of conventional benzocyclobutene (BCB) is insufficient to suppress current collapse because water molecules easily permeate BCB, especially when using a cavity-gate structure. On the other hand, the moisture resistance of MSQ is very high because of the excellent hydrophobic property, and the current collapse due to moisture was effectively suppressed. So, improving the moisture resistance with hydrophobic low-k films plays a key role in reducing the current collapse of GaN HEMTs, especially when using a cavity-gate structure. Moreover, the parasitic capacitance of GaN HEMTs was successfully reduced by using the MSQ-cavity, and RF performance was improved by around 20%.

S5-H7: GaN-HEMT technology for high power millimeter-wave amplifier

In this work, we developed (1) an offset-overhanging Y-shaped gate structure to reduce the electric field at gate-edge, and demonstrated (2) low current collapse of InGaN back barrier structure that improved off-state breakdown voltage. In addition, we adopted (3) an InAlN electron-supplying layer to enhance the drain current. The fabricated InAlN/GaN HEMTs with 80-nm gates showed a high off-state breakdown of 73 V, a high drain current of 1.2 A/mm and a high Pout density of 1 W/mm at 90 GHz.

X-Ku Wide-Bandwidth GaN HEMT MMIC Amplifier with Small Deviation of Output Power and PAE

A new design methodology was proposed to obtain wide-bandwidth and flat-group-delay reactive-matching GaN HEMT MMIC amplifiers. Frequency dependence of the optimal source and load impedance of a GaN HEMT are derived as polynomial equations and matching circuits are designed by small signal simulation without the use of large-signal transistor model and large-signal simulation. Fabricated GaN HEMT MMIC amplifiers, which show a small deviation of Pout and PAE in the range of 8-18 GHz, prove that our methodology is suitable for the design of a wide-bandwidth MMIC amplifier.

Q-Band InAlGaN/GaN LNA using current reuse topology

A 33 to 41-GHz Low Noise Amplifier (LNA) with a 3-dB Noise Figure (NF) using 0.12-μm InAlGaN/GaN HEMT was developed. The LNA consists of a two-stage common-gate amplifier with current reuse topology in order to obtain a high gain with low power consumption. The developed LNA achieved 15-dB gain, and an input return loss of less than -10 dB. The measured NF was 3 dB, and the power consumption was 280 mW. The measured OIP3 and OP1dB were 24 dBm and 13 dBm at 38 GHz under a supply voltage of 20 V. The chip size of the LNA is 1 × 0.7 mm2.

InAlGaN/GaN-HEMT device technologies for W-band high-power amplifier

We demonstrated an excellent output power (Pout) density performance using a novel InAlGaN/GaN-HEMT with an 80-nm gate for a W-band amplifier. To eliminate current collapse, a unique double-layer silicon nitride (SiN) passivation film with oxidation resistance was adopted. The developed discrete GaN-HEMT achieved a Pout density of 3.0 W/mm at 96 GHz, and we fabricated W-band amplifier MMIC using the air-bridge wiring technology. The Pout density of the MMIC reached 3.6 W/mm at 86 GHz. We proved the potential of the developed InAlGaN/GaN-HEMT experimentally using our unique device technology. With the aim of future applications, we developed a novel wiring-inter-layer technology. It consists of a cavity structure and a moisture-resistant dielectric film technology. We demonstrated excellent high-frequency performances and low current collapse originating in humidity-degradation using AlGaN/GaN-HEMT. This is also a valuable technology for InAlGaN/GaN-HEMT.

Heterogeneous Integration of Microwave GaN Power Amplifiers With Si Matching Circuits

GaN high electron mobility transistors were integrated into monolithic microwave integrated circuits (MMICs) by molding hetero-substrates and using a redistribution layer (RDL). Driver amplifiers (DAs) and high-power amplifiers (HPAs) on SiC substrates were molded with matching circuits on Si substrates including Cu-filled through-substrate vias (TSVs), and their circuits on hetero-substrates were connected using a Cu RDL. This was the first attempt to fabricate hetero-substrate MMICs with five chips for two-stage power amplifiers. This method will be very useful to increase the achievable quantity of small DAs and HPAs—as opposed to using large MMICs with matching circuits on a SiC substrate—and to reduce production costs. Furthermore, various frequency bands, such as the millimeter-wave band, can be accommodated by changing the Si chips of the matching circuits.

High-Power-Density InAlGaN/GaN-HEMT Technology for W-Band Amplifier

We demonstrated an excellent output power (Pout) density performance using a novel InAlGaN/GaN-HEMT with an 80-nm gate for a high-power W-band amplifier. The developed HEMT showed basic reliability for commercial products. A unique double-layer silicon nitride (SiN) passivation film with oxidation resistance was adopted to suppress current collapse. The developed discrete InAlGaN/GaN-HEMT achieved a Pout density of 3.0 W/mm at 96 GHz, and the Pout density of MMIC reached 3.6W/mm at 86 GHz. We proved excellent potential of developed InAlGaN/GaN-HEMT using our unique device technologies. Furthermore, we suggested the physical advantage of the InAlGaN/GaN-HEMT structure using device simulator.