Abstract
Recently, the researches of GaN-based HEMTs for high speed and high power devices become more and more popular owing to its wide band-gap, high critical electric field, high electron saturation velocity, and good thermal conductivity. In addition, the AlGaN/GaN transistor grown on Si substrate gain ground nowadays, although its property may not be as well as on SiC and sapphire substrate. However, GaN-on-Silicon is promising as the one of mainstream technology in the future when considering cost and the capability of CMOS integration. In this thesis, we improve the characteristics of AlGaN/GaN devices for high frequency and high power applications by changing the layout both horizontally and vertically. First, by using E-beam to scale down the source-drain distance and using the hybrid electrode structure for horizontal layout, we can effectively improve the devices performance for high frequency and high power applications simultaneously, including the f_T up to 40 GHz, the f_max up to 64 GHz, the g_m "of 187 mS" ⁄"mm", the I_d "of 877mA" ⁄"mm", and the VBK of 39 V between gate and drain. In addition, we can obtain the intrinsic parameters and alter our layout structures for the better device properties according to the simulation of equivalent circuit model. Second, by using Ge diffusion for vertical layout, we can further improve the turn-on voltage, the leakage current, and the breakdown voltage in SBDs for high power applications. The Von can be improved up to 22%, the VBK can be improved up to 257%, and the leakage current can be suppressed about one order of magnitude. In conclusion, the results indicate that the high power characteristics can be improved without changing the area of horizontal active region.