Growth of thick GaN film with low dislocation density on Si(111) substrate by inserting LT-AlGaN interlayer and HP-GaN nucleation layer

• Main Authors: Huang, Kun-Sung, 黃坤松
• Other Authors: Chang, Edward Yi
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/eg83gx

碩士 === 國立交通大學 === 光電系統研究所 === 105 === GaN shows many superior physical properties such as wide bandgap, high carrier velocity, high breakdown field and good thermal conductivity. Therefore, normal AlGaN/GaN HEMTs show characteristics of high breakdown voltage and high current. Furthermore, normal AlGaN/GaN HEMTs can be grown on large-sized Si substrate, so the fabrication cost can be reduced significantly. Accordingly, GaN material is a candidate for replacing Si-based devices to become next-generation high-power electronics. However, it is necessary to have high breakdown voltage for high power device applications. For epitaxial growth, you must have the thick and high quality gallium nitride epitaxial layer. In this study, in order to grow thicker GaN epitaxial layer, a LT-AlGaN interlayer was inserted. Use different growth temperature and growth time of LT-AlGaN to obtain the best parameter of LT-AlGaN interlayer. The 2.8 μm crack-free epilayer was grown with optimization of LT-AlGaN for 200 seconds at set temperature of 950°C. From rocking curve scan of XRD analysis, FWHM of GaN (002) was 530 arcsec and GaN (102) was 872 arsec. Finally, HP-GaN nucleation layer was inserted to this structure to further improve the quality of the gallium nitride epitaxial layer and enhance the performance of AlGaN/GaN HEMTs. At last, the result shows FWHM of GaN (002) and (102) were 348 arcsec and 506 arcsec, respectively. Breakdown voltage of the device obtains from the measurement for 3 and 5 µm spacing were 90 V and 170 V, respectively. At 36 μm spacing, the breakdown voltage was as high as 550 V. The results demonstrate that inserting LT-AlGaN interlayer can increase the thickness and improve the quality of film. Finally, HP-GaN nucleation layer was inserted to this structure to further improve the quality of the gallium nitride epitaxial layer and enhance breakdown voltage of AlGaN/GaN HEMTs.