| dc.description.abstract | It is the goal that the global various countries have wanted to reach all the time to pursue the electric supply and demand of high quality, a large number of construction power plants do not solve the way of the problem, but should improve the efficiency of the electric equipment products. In this thesis, we studied on GaN Schottky diodes with mesa-type n-GaN and planar-type AlGaN/GaN, operating at high forward current and high breakdown voltage. In Mesa-type n-GaN Schottky diodes, having a drift region of 2.8?m thickness and doping concentration of 5×1016/cm3, show a breakdown voltage of about 190V. We report I-V characteristics, both at room temperature and in the temperature range 300 to 423K, of Mesa type GaN Schottky diodes fabricated on expitaxial layers incorporating double GaN/SiN nucleation layers.
For a more significant reduction of the on-state resistance, AlGaN/GaN heterostrure devices are attractive due to their high mobility and high carrier density of two-dimensional electron gas at the AlGaN/GaN interface. In planar-type AlGaN/GaN Schottky diodes, we studied simulation and fabrication of AlGaN/GaN rectifiers with field plate termination. The extent of metal electrode overlap and dielectric thickness were varied to ascertain their effects on the BV. The circular devices show on-resistance (Ron) of about 13m?-cm2. The experimental breakdown data shows that there is an optimum Si3N4 thickness for which the breakdown voltage (BV) is highest and on either side of this optimum Si3N4 thickness, the BV voltage decreases. In the present case, the highest BV of about 475V is obtained when silicon nitride thickness is around 800nm and the Schottky diodes exhibit a figure of merit (VB2/Ron) of about 17MW/cm2. The 40 finger-type AlGaN/GaN Schottky diodes with wire bonding obtained a forward current 2.5A at an applied forward voltage of 3.5V, and BV of about 436V. In reverse recovery characteristics of the finger-type AlGaN/GaN Schottky rectifiers, when the diode was switched from forward to reverse bias, the device exhibited an ultrafast switching time (trr) 15ns less than 30ns of Si-based device. | en_US |