(Invited) Ultra-Wide-Bandgap Semiconductors for Power Electronics
This talk will focus on our efforts to develop the Aluminum Gallium Nitride (AlGaN) system with Al composition in the range of 30-100% into a viable material for next-generation power electronics. The basic advantages of AlGaN relative to Si, SiC, and GaN will be discussed, as evidenced by the superior unipolar Figure-of-Merit (FOM) for AlN as demonstrated in Figure 1. Here, AlN is shown to have a theoretical order-of-magnitude improvement relative to GaN; in the plot, high breakdown voltage (VB, horizontal axis) and low specific on-resistance (Ron,sp, vertical axis) are desired. This FOM is based on a number of basic material parameters such as mobility and critical electric field, which will be covered in the talk. Fundamental challenges associated with substrates, epitaxial growth, doping, and point and extended defects will be discussed. Vertical and lateral (heterostructure-based) device architectures will likewise be covered, and the advantages and limitations imposed by the properties of the UWBG AlGaN materials will be examined. In particular, it will be demonstrated that an intrinsically normally-off device that exceeds the capability of GaN (as measured by the FOM) is viable. Experimental results at both the material and device levels will be presented.
This work was supported by the Laboratory Directed Research and Development (LDRD) program at Sandia. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.