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Some Examples of Our Current Research Thrust

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Our experience with Vertical GaN since 2006 is coming to fruition with avalanche-capable devices. Thanks to the highest quality material and edge termination.
A vertically integrated lab allows us to grow material, fabricate devices, and characterize them in circuits.

High Power Electronics: Exploring the limit that GaN can offer in voltage is of great interest to the Power Electronics community. We are working on developing high voltage devices to be able to answer key questions, including the fundamental ones!

The first demonstration of a bulk GaN switching device in the form of a Current Aperture Vertical Electron Transistor (CAVET) helped establish the need for vertical GaN device research. 

High-Frequency Electronics: Over the last 50 years we have witnessed a continuous improvement in device, circuit, and system performance opening up new possibilities of application. The advancement shifted from initially being dynamic to being incremental and now plateauing as the materials (mainly Si) reach their theoretical limits. When the transistor gate length decreases below 50 nm, the parasitic capacitances and resistances become dominant, creating a “performance gap” that limits the transistor delay and hence the operating frequency. Gate length reduction, the main technology that has enabled today’s electronics, is no longer sufficient to push the limit further. The performance gap preventing operations at terahertz or near terahertz regime makes the development of ultra-broadband wireless communication, advanced imaging, and radar, electronic THz spectroscopy, or THz digital computation increasingly difficult. Is it the ultra-scaled ballistic device that can fill in the THz-gap? We are trying to answer this through novel device designs

Ultra-Scaled Pillars for High-Frequency Devices

Developing Diamond Technology for Active Cooling of RF GaN Devices: 5G enables unprecedented levels of connectivity, upgrading 4G networks with five key functional drivers: ultra-fast broadband, reliable low latency communication massive machine-type communications, high reliability/availability, and smart energy usage. These features will redefine manufacturing, transportation, public services, and health. Are we prepared for 6G and up? GaN transistors are exciting, but heat degrades their performance.

Thermal Management is crucial to make GaN devices deliver the highest power density the material properties promise. We are looking into diamond integration for heat spreading in GaN HEMTs.


Integration of diamond on GaN can ease the challenges associated with thermal management of GaN-based power amplifiers which need to base on highly scaled transistors to push toward higher frequencies at high powers for 5G networks. Due to the incompatibility of conventional diamond growth recipes with thin dielectrics (< 5 nm) a novel growth recipe was designed for polycrystalline diamond integration on top of GaN high electron mobility transistors. Our growth recipe maintains device performance and no physical damage can be observed at the interface. We measured the difference in the channel temperature, which decreased by more than 100 oC in the range of 10-24 W/mm power after the integration of diamond on top of the device.

Record-Low Thermal Boundary Resistance between Diamond and GaN-on-SiC.


STEMs and EDS results of PC diamond grown on N-polar GaN HEMT on SiC substrate. STEMs show a smooth diamond/Si3N4/GaN interface and EDS confirms SiC formation between diamond and Si3N4.

SEM micrograph of the fabricated device with diamond integrated on top of the channel. Channel temperature measured using I-V thermometry versus power dissipated into the channel for devices with and without diamond, confirming a lower channel thermal resistance for the sample with diamond.

Recent News From Semiconductor Today: "Diamond for Ga2O3 Thermal Management"
Research Review from Compound Semiconductor: "Tackling Gallium Oxide's Poor Thermal Conductivity with Diamond Layers"


Schottky Junction Vertical Channel GaN Static Induction Transistor with a Submicron Fin Width:
This work introduces the GaN-based static induction transistor, which is a unique transistor in operation without any p-type GaN and gate dielectrics for its functioning, with its process strategy and electrical performance. Examined current density and modulation depending on the sub-micrometer fin channel reveals that the reduction in fin size could increase the current modulation while decreasing current density because of the raising in potential minima by the overlap of the depletion region.


Study on the First Derivative Output Properties of GaN Static Induction Transistor with Sub-micrometer Fin Width:
This work addresses the fundamental electrical properties of a Schottky-junction vertical channel GaN static induction transistor based on the analysis of the first derivative of its output curve. The results cover the unique properties of the conduction mechanism in a sub-micrometer channel and the device electrostatics governed by the external biases to control the electrical performance of the device.