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Strategic Research Initiatives

Wide-Bandgap (WBG) Power Electronics Research Initiative Toward A Center Of Excellence And Entrepreneurial Opportunities

Kyekyoon (Kevin) Kim (217-333-7162), Elyse Rosenbaum, and Philip T. Krein, Electrical and Computer Engineering

Addressing the Problem

Ever since the team first grew GaN on sapphire using a plasma-assisted ionized source beam in 1995, the Thin Film and Charged Particle (TFCP) Lab, under PI Kim’s direction, has pioneered plasma assisted molecular beam epitaxy (PAMBE) as an enabling technology for the growth of high-quality GaN-based thin films for optical, power, and other electronic devices. This technology has progressed and matured to the point that we can uniquely process state-of-the-art devices, especially high-power electronic devices. Technical innovations and recent achievements include: 1.) selective-area growth (SAG) by PAMBE, 2.) sputtered gate-SiO2, 3.) sputtered single-crystal AlN on Si, and 4.) transfer printing via pre-etched SOI wafer.

Research Goals

The researchers further expand on this existing technical base and join with leaders in related areas from The Grainger College of Engineering to strategically establish a technological alliance to lead world-class GaN-based power electronics research. The most significant outcomes of this project will be:

  • Optimization of the PAMBE-SAG process for regrowth of p/n+ GaN on bulk GaN template without trench etching or damage;
  • Development of gate insulation technologies for GaN devices;
  • Backside processing to obtain low on-resistance;
  • Optimization of junction termination extension by systematic design/simulation;
  • Development of a lifetime projection methodology;
  • Integration of GaN MPS (Merged PiN-Schottky di-ode) with GaN MOSFET for power converter and inverter applications.

Current Activities

Specific project tasks include:

  • Improvement of ohmic contacts using SAG;
  • Development of gate insulation;
  • Development of backside processing for low on-resistance;
  • Optimization of termination structure for high power density;
  • Investigation of wear-out mechanisms for GaN devices in power converters.

Results to Date

Achievements during the first year include:

  • Design of high-performance power HEMTs and MOS-HEMTs and fabrication of corresponding masks;
  • Evaluation of other candidate gate dielectrics (non-SiO2) such as Al2O3, HfO2, and TiO2; Optimization of MOS-gated HEMT using various gate insulators;
  • Reliability analysis of SiO2-based GaN MOS-HEMTs, grown on a variety of substrates;
  • Initiation of work on vertical devices prompted by the reliability study on lateral devices.