[Updated on April 11, 2017] Dear colleagues:

I am excited to share with you a bit about growing customer interest in Kyma’s gallium oxide (Ga2O3) epitaxial wafers (epiwafers) and epitaxial growth services.

As background, Ga2O3 has several polytypes, referred to in the literature as the α-, β-, γ-, δ-, and ε-phases, with β-Ga2O3 being the stable phase under standard temperature and pressure (STP) conditions. Thus the non-β-phases of Ga2O3 are metastable. β-Ga2O3 substrates can be grown from the melt a lot like sapphire can and thus have been proven to be much easier to produce than their distant GaN cousins. β-Ga2O3 has a monoclinic crystal structure, a relatively wide bandgap of 4.85eV, and a relatively low thermal conductivity that is in the range of 10 to 20 W/mK depending on crystallographic direction. There are many additional attributes (e.g., good electron mobility, high critical field, ability to add Al to make heterostructures) of the Ga2O3 materials system that translate to very high figures of merit for power electronics applications, as well as plenty of challenges (e.g., its relatively low thermal conductivity and the fact that p-doping attempts are so far unsuccessful). Because of its great potential, the literature about the materials properties, and device and other applications of Ga2O3 is rapidly growing. A good starting point for reading up on Ga2O3 is the article entitled “GALLIUM OXIDE: PROPERTIES AND APPLICATIONS – A REVIEW,” published in 2016 by Stepanov, et al., in "Reviews on Advanced Materials Science.

Kyma first announced the launch of its Ga2O3 epiwafer product line in March 2016. At that time this new product offering was centered on homoepitaxial β-Ga2O3 epiwafers – i.e., epitaxial β-Ga2O3 grown upon crystalline β-Ga2O3 substrates. Interest in Kyma’s β-Ga2O3 epiwafers has been good, in part due to the recent availability of β-Ga2O3 substrates, which Kyma can now procure or customers can procure them separately and then provide them to Kyma.

Yet those substrates are limited in terms of their size, cost, and form factor. Not to be held back, a growing number of researchers as well as a new startup company are seeking alternative paths to exploit the Ga2O3 materials system. We point to three recent examples of such: 1) a few companies are pursuing the addition of β-Ga2O3 substrates to their product line, 2) several R&D groups are studying the materials characteristics and device potential of heteroepitaxial Ga2O3 wafers – i.e., wafers created by growing Ga2O3 on non-Ga2O3 substrates such as sapphire (α-Al2O3), silicon, and silicon carbide (SiC), and 3) FLOSFIA Inc., a very new startup spun out from KYOTO University, has announced on its website that it aims to “develop its own production lines and commence commercial production of the world’s first α-Ga2O3 power device in 2018” which the company realizes using an innovative MIST CVD technology to grow α-Ga2O3 on α-Al2O3 – we note that α-Al2O3 is the stable phase of sapphire.

As a result of these market and technology currents, Kyma is experiencing a growing number of customer inquiries seeking heteroepitaxial Ga2O3 wafers, which Kyma offers on a best efforts basis. With the interest in heteroepitaxial wafers growing, Kyma is working to better quantify our capabilities in hopes of moving beyond best efforts and putting detailed specifications in place. We plan to update our Ga2O3 materials product page accordingly as we continue to advance our understanding of customer interests and our capabilities to satisfy them in this dynamic and promising yet early stage technology space.

Kyma will present an update of some of recent company advances in the growth and characterization of Ga2O3 epiwafers at the upcoming 32nd Annual CS ManTech Conference. Kyma's paper is co-authored by several colleagues at Air Force Research Laboratory (AFRL) Sensors Directorate and Northrop-Grumman Synoptics, and is entitled "Development of Homoepitaxial Growth of β-Ga2O3 by Hydride Vapor Phase Epitaxy."