| Summary: | 碩士 === 國立交通大學 === 照明與能源光電研究所 === 102 === In this thesis, we used a horizontal home-made hydride vapor phase epitaxy (HVPE) to grow thick GaN layers on a sputtered AlN/patterned sapphire substrate. We initially optimized surface morphology and crystal quality by changing the V-III ratio to acquire a smooth surface. Next, we attempted to induce the sputtered AlN into becoming a buffer layer to realize one-step growth in HVPE and then applied this technique to the patterned sapphire substrate. Results showed that the GaN films grown on the patterned sapphire substrate had a rough surface. Thus, we induced a two-step growth epitaxy technology and successfully improved the morphology and quality of the GaN film. We then used optical microscopy, scanning electron microscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy to measure surface morphology, epitaxial layer thickness, and crystal quality. The 10 μm-thick GaN template had lower etching pit density (from 1.7108 cm−1 to 8.8107 cm−1) and smaller FWHM (from 726 arcsecs to 325 arcsecs) than the 2 μm-thick GaN template from MOCVD.
We also applied a thick GaN template to GaN-based light-emitting diodes (LEDs). Compared with the light output power of the LED device grown on the 2 μm-thick GaN template, that of the LED device grown on the 10 μm-thick GaN template was enhanced by 89% at an injection current of 20 mA. The saturation current of the LED device grown on the 10 μm-thick template also improved from 300 mA to 405 mA when compared with that of the LED device grown on the 2 μm-thick GaN template. These results can be explained through thermal imaging. This thesis provides a suitable GaN template for LED devices.
|
|---|
