| Summary: | The thesis aims at investigating the state-of-the-art The Insulated Gate Bipolar Transistor (IGBT) technologies and exploring novel device concepts based on the IGBT core in order to enhance device performance and functionality. First, a novel double gate IGBT (DG-IGBT) is demonstrated by numerical simulations and experimental verifications. The new device features a low-grain pnp transistor and an embedded thyristor to enhance the carrier concentration near the emitter side and thus improves the on-state performance. Second, a new IGBT structure featuring N+ islands in the buffer layer to control the on-state carrier density in the drift region is proposed. The new technique allows a precise control of the trade-off between on-state voltage drop and turn-off energy losses by simply adjusting the width and spacing of N+ islands on the mask (at the layout level rather than process level). Furthermore, the N+ islands technique can be used to produce a series of products with different specifications by only changing the mask layout. Finally, a new reverse-conducting IGBT (RC-IGBT) with an embedded thyristor is reported in this dissertation for the first time. The thyristor operates similarly to an anti-parallel diode in its on-state and therefore it can release stored energy in the inductive load when the IGBT turns off. The new RC-IGBT shows a “snapback-free” characteristic due to the existence of the thyristor. In addition, coupled with the N+ islands structures proposed before, the on-state performance and switching speed of the IGBT and thyristor can be optimised according to the requirements of the specific application.
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