Fabrication of novel monolithic optical devices composed of blue laser diodes and ferroelectric optical waveguides

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In order to develop novel monolithic optical devices composed of blue laser diodes and ferroelectric optical waveguides, ferroelectric lead zirconate titanate (PZT) films were deposited on gallium nitride (GaN). PZT films were deposited by pulsed laser ablation on cubic GaN prepared on (001) GaAs by metalorganic vapor phase epitaxy for the first time. PZT films were preferentially [100] oriented on GaN with MgO buffer layers although PZT films were randomly oriented without MgO buffer layer. The origin for the difference is thought that MgO buffer layer acts as a diffusion barrier between PZT and GaN.Relationship between the crystallinity and the resistance against oxidation was also studied. It was found that GaN with lower crystallinity shows higher resistivity. It was also revealed that the crystallinity degrades and the surface roughness decreases both with an exposure to oxygen atmosphere around 500 ℃.