Nanocasting of High Surface Area Mesoporous Ga₂O₃ and GaN Semiconductor Materials

We report mesostructured gallium oxide and nanoporous gallium nitride, synthesized via a nanocasting technique using mesoporous carbon as template. The carbon template is first loaded with a gallium chloride toluene solution to generate a Ga precursor/carbon composite. Gallium oxide is generated by reaction of the composite in air during calcination, which also eliminates the carbon template. Formation of mesostructured Ga 2 O 3 requires a two-stage oxidation reaction, first at 450 °C and followed by 500 °C. X-ray diffraction, nitrogen physisorption, and transmission electron microscopy show the Ga 2 O 3 products to be mesostructured with a very high surface area of 307 m 2 /g and pore volume of 0.54 cm 3 /g. The Ga 2 O 3 exhibits a band gap energy of 4.6 eV. Thermal treatment of the Ga/carbon composite in the presence of ammonia (i.e., nitridation) generates crystalline nanoporous GaN with surface area of 136−156 m 2 /g and pore volume of 0.3−0.4 cm 3 /g.