Wide bandgap materials, such as GaN and SiC, have been rapidly maturing for use in power electronic applications. Recently, there has been a push to investigate materials with ultra-wide bandgaps (E_g > 3.4eV), such as Ga₂O₃ and AlGaN, in an attempt to achieve higher critical electric field, as it scales with the bandgap to the >2 power. Increasing the Al-content of AlGaN has been pursued for several applications, including both power electronics and UV optoelectronics, as the bandgap, and thus critical electric field, of the material increases with increasing Al-content. Though decades have been spent maturing GaN and low Al-content AlGaN for power, RF, and optoelectronic applications, the path for fabricating devices utilizing Al-rich AlGaN is not as straightforward as one may hope.

An overview of Sandia National Laboratories’ device development with Al-rich AlGaN will be presented. In addition, this talk will report on the intricacies faced during fabrication of Al-rich AlGaN devices, including both the challenges and advancements that AlGaN can present such as the effects of Al content on dry etch characteristics (e.g. surface morphology and etch rates), effects of surface cleaning and preparation, as well as metallization schemes and characteristics for both Schottky and Ohmic contacts.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.