The need for robust, high performing devices in the defense market continues to drive innovation and progress in materials research. These devices require high power density, voltage capacity and switching frequency—all while withstanding high junction temperatures (> 200 °C). Bulk Aluminum Nitride (AlN) substrates are an attractive solution for next generation devices due to their high thermal conductivity, ultrawide bandgap, close lattice matching with other III-N (AlxGa1-xN), and low dislocation density.
Traditionally, AlN has been used in the optoelectronics market to produce high power UVC LEDs which emit at the 265 nm wavelength—the optimal wavelength for disinfection. AlN substrates with low absorption coefficient in the UV-regime also allow for a more efficient light source for disinfection.
UVC LEDs are gaining traction as a replacement for legacy mercury UV lamp technology in point-of-use and point-of-entry water treatment, which require more than a million LEDs per year. To meet the needs of these markets, there is an ecosystem of AlN providers producing multiple thousands of high quality 2-inch AlN substrates per year. This has led to the commercial availability of these substrates for electronic device development.
However, the industrial deployment of AlN for applications in RF and power devices requires much larger diameters to take advantage of existing fab capabilities and to meet the end device cost models. Key to the adoption of this substrate technology in defense and commercial electronic applications is the availability of increased substrate diameter, 100 mm being the minimum for some modern foundries. Efforts by several groups to increase the AlN crystal diameter and maintain high crystalline quality has been undertaken, however the general common misconception is that commercially viable 100 mm bulk AlN is nowhere near ready.
However, that is simply not the case anymore. Crystal IS first announced the successful growth of a 100 mm diameter boule in summer 2023—with a follow-on announcement of improved crystal quality that achieved a 99% substrate usable area based on the current requirements for optoelectronic devices. These 100 mm substrates are now readily available for research projects as we continue in parallel to improve quality and manufacturability of this technology.
Read more on our approach to develop the 100 mm AlN single-crystal substrates in our recent article on Physica Status Solidi B here.