Abstract: Semiconductor devices each include: a semiconductor substrate that contains beta-gallium oxide and has a first conductivity type; a first semiconductor region that contains beta-gallium oxide, has the first conductivity type, and is provided on an upper side of the semiconductor substrate; a second semiconductor region that contains beta-gallium oxide, has a second conductivity type, and is provided on an upper side of a part of the first semiconductor region; and a third semiconductor region that contains beta-gallium oxide, has the first conductivity type, and is provided on an upper side of a part of the second semiconductor region. When the first conductivity type is an n-type and the second conductivity type is a p-type, the second semiconductor region further contains a band gap control element. The band gap control element is selected from a group of boron, aluminum, and indium.

Abstract: A method for making &ggr;-alumina includes drying wet alumina gels at temperatures and pressure below those commonly present in preparation of &ggr;-alumina. The method allows for production of &ggr;-alumina with greater ease of production and controllability of physical properties than known methods. Alumina produced using this method has high surface area and porosity and is highly suitable for making &ggr;-alumina powders for use as catalyst supports.