Research On Key Techniques Of Gate Commutated Thyristor (GCT)

Gate commutated thyristor (GCT) is a new high power semiconductor devices based on Gate turn-off thyristor(GTO), GCT has extensive application foreground and it is a blank in interiorly now. In this thesis, the differences of GCT and GTO in structure, principle, characteristics and fabrication process are analyzed systematically. In views of the p base region, n field stop layer, transparent anode region and isolation region, the characteristics of GCT are analyzed by MEDICI simulator. The three improved structures are presented, and the optimum design of key structural parameters is done. Simultaneously, the fabrication process of GCT is analyzed by ISE-TCAD software, and the process implementation scheme is validated by the experiment results. The main content is as follows:Firstly, the breakdown mechanism of GCT is studied. The result shows that the breakdown of GCT is field stop (FS) breakdown essentially, but not the punch through (PT) breakdown. It is pointed out the perspective for the GCT breakdown mechanism had localization ago. And the blocking characteristic of GCT is simulated and analyzed, the design method and optimal structural parameters are given.Secondly, the current transport mechanism of transparent anode is studied. The expression of electron current density at transparent anode are derived, and the variations of the electron and hole injection efficiencies of transparent anode with the anode current density are given. The characteristic of transparent anode is compared with that of conventional anode and short anode, the results show that the transparent anode used in GCT can improve the switching characteristic.Thirdly, the structural features and fabrication process of GCT are analyzed. The results show that the transparent anode, FS layer and the selective p-diffusion are difficult to use conventional process. And because a curvature junction exists in RC-GCT, it results in the fall of the breakdown voltage of device, and the increase of the cost and the complexity of fabrication process of RC-GCT device. In order to solve these...