Yoichi Kamada

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.