Improvements of Vertical Conductive GaN LEDs Using Novel Materials
| Autor: | Wei-Cheng Kao, 高偉程 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 In this thesis, the vertical type GaN LEDs have been fabricated by metal bonding process using electroless plating gold (Au) and deposition of a diamond like carbon (DLC) thin film incorporated in the device. To fabricate thin GaN LEDs device, the sapphire substrate was removed by laser lift-off technique and the LED structure was transferred to Si wafer. For vertical LED with DLC layer, the material characteristics of bonding layer, performances of device and thermal analyses have been investigated. Moreover, the characterizations were compared with those of vertical LED without DLC layer and conventional lateral LED. For the fabrication of vertical type GaN LED, a mirror was grown on epilayer structures and annealed. Then a DLC layer deposited by sputtering and an Au layer grown by electroless plating were prepared in sequence on the mirror. Furthermore, the Au layer and In/Au layer on Si wafer were interdiffusion to form Au/In/Au layer at 220 °C. It indicated that the Au layer with good uniformity and roughness was helpful to bond with In/Au layer. At an injection current of 700 mA, the output power and light extraction efficiency of vertical LED with DLC layer were 461 mW and 16%, respectively. Moreover, the light extraction efficiencies of vertical LED without DLC layer and conventional lateral LED were measured to be 13.9% and 8.5% (@ 700 mA), respectively. It reveals that the vertical LED with DLC layer has a significant improvement in the light extraction efficiency. For the vertical LEDs with and without DLC layer and conventional lateral LED, the surface temperatures were measured to be 61, 70.5 and 83.2 °C, respectively. Meanwhile, the thermal resistances of these samples were 13.2, 19.1 and 22 K/W, respectively. It indicates that the LED device with DLC layer exhibits high performance in heat dissipation, resulting in the good electro-optical property and thermal stability. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|