Jun-Sik Park

A study of transparent indium tin oxide (ITO) contact to p-GaN

Abstract In this study, indium tin oxide (ITO) thin film was evaporated on Mg-doped p-GaN layers with low 10 17 /cm 3 , grown by metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire wafers, and its contact properties were investigated. The sheet resistance ( R S ) of the evaporated ITO films was several kΩ/□ before the annealing but the sheet resistance decreased to 40–50 Ω/□ after the annealing in N 2 using a rapid thermal annealing (RTA) system. I – V characteristics and contact resistivities of the evaporated ITO on p-type GaN were investigated as a function of substrate treatment, annealing time, and annealing temperature. The results showed that, in optimized conditions, the ITO contacts with the resistance in the range of low 10 −1 Ω cm 2 could be obtained, and which is probably applicable as the ohmic contact for GaN-based light emitting diodes. Also, at these conditions, the measured optical transmittances of ITO film were above 90% at a wavelength of 420 nm (blue).

Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films

Here we report a photonic annealing process for yttria-stabilized zirconia films, which are one of the most well-known solid-state electrolytes for solid oxide fuel cells (SOFCs). Precursor films were coated using a wet-chemical method with a simple metal-organic precursor solution and directly annealed at standard pressure and temperature by two cycles of xenon flash lamp irradiation. The residual organics were almost completely decomposed in the first pre-annealing step, and the fluorite crystalline phases and good ionic conductivity were developed during the second annealing step. These films showed properties comparable to those of thermally annealed films. This process is much faster than conventional annealing processes (e.g. halogen furnaces); a few seconds compared to tens of hours, respectively. The significance of this work includes the treatment of solid-state electrolyte oxides for SOFCs and the demonstration of the feasibility of other oxide components for solid-state energy devices.