Some Examples of Our Current Research Thrust
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!
CAVET: Current Aperture Vertical Electron Transistor (look into our publications for more)
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” which 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
Exploring Ultra-Wide Bandgap Material – Like Diamond!
Diamond presents outstanding semiconductor properties that have long been recognized for high power, high frequency, and low noise applications. With a bandgap of 5.47 eV, diamond is an insulating material when undoped. However, when terminated with hydrogen, the C–H bond at the terminated surface creates a dipole layer that induces a negative electron affinity reported to be as low as –1.3 eV and a concurrent lowering of the ionization energy to 4.2 eV has led to significant interest in electron emission devices due to the ease with which electrons excited into the conduction band can be emitted from the surface. Moreover, it drives the transfer of electrons from the diamond valence band into the accepting state of an appropriate adsorbate layer on the diamond surface giving rise to p-type surface conductivity carried by a resulting subsurface hole accumulation layer. The layer extends a few nanometers into diamond and supports a carrier density of up to 4 x1013. The rich physics that characterizes Diamond’s unique properties such as 1) Negative electron affinity, 2) Surface conductivity and 3) Surface reconstruction need complete understanding, only possible with careful experimentations. Our group’s work on Diamond since 2014 under ARPA-E SWITCHES and DARPA YFA programs have established promising device performances that form the seed to our current work on Diamond!
Diamond Growth Under Microwave Plasma in CVD
We work towards developing GaN vertical technology to provide a solution for next-generation power conversion. We also explore the extreme frequency limits possible with highly scaled GaN devices. Beyond GaN, we are looking into Diamond and other III-Nitrides. Most importantly, we are inventing new devices to offer functionalities in systems, not even thought of before.
The WBG Lab is looking for a Postdoc with processing expertise / Stanford Ph.D. student with interest in processing. For more information, please see the link below.