Abstract
The properties of gallium nitride are suitable for operation under high temperature and high voltage, mainly because of the wide bandgap(3.4eV), good thermal stability, high critical electric field(3.4MV/cm),and high electron saturation velocity(2×107cm/s) of the material. These advantages make gallium nitride excellent for the applications of high frequency and high power devices. The gallium nitride based device such as high electron mobility transistor (HEMT) and Schottky barrier diode (SBD) have been widely discussed and developed in recent years. Especially, the GaN-on-Silicon devices with the compatibility of CMOS process attract significant attention. This thesis presents the study of AlGaN/GaN Schottky barrier diodes on the silicon substrate, involving device design, manufacturing, measurement and, analysis. There are two main topics included in this thesis. Frist, the AlGaN/GaN SBDs with nitrogen plasma treatment and Schottky recess is discussed. The turn-on voltage can be decreased from 0.9 V to 0.35 V, and the leakage current decreased from 10-5A/mm to 107A/mm by using nitrogen plasma treatment with 30W at 300C. The proposed method effectively improves the leakage current and reduces the surface nitrogen vacancy and other related defects. After treatment, the device sheet resistance decreases by about 50Ω/□ with a relatively small on-resistance. A large forward current and breakdown voltage over 1100V can be achieved. Another topic is the SBDs with a dual Schottky metal anode. The use of a low work function -of titanium can reduce the turn-on voltage of the diode. On the other hand, the nickel as a high work function can suppress the leakage current. This dual-metal structure effectively reduces the turn-on voltage from about 1.2 V to 0.8 V. But the devices suffer an increased leakage current by about two orders to be about 10-5A/mm, compared with the traditional single nickel anode devices, due to the smaller equivalent Schottky barrier height. Therefore, the larger ratio of Ti/Ni of the anode results in larger leakage current and smaller VON. In contrast, with a smaller ratio of Ti/Ni, the leakage current can be suppressed. .