In the current field of medium voltage and high power application, the dominant power semiconductor devices mainly include thyristor, gate switchable thyristor (GTO), insulated gate bipolar transistor (IGBT), etc. These traditional power devices have some defects in practical aspects. Gtos are assembled into thousands of separate switch units on a single silicon chip. At medium voltage, GTO presents small on-state loss and reasonable off loss. However, due to the uneven switching, the GTO requires an external buffer circuit to maintain operation. These buffer circuits occupy most of the volume of the whole equipment, which is the main cause of complicated design, high cost and large loss.
On the contrary, the IGBT switch uniform, do not need buffer circuit, but the on-state loss is large, and used in the medium voltage circuit, must be used in series low-voltage IGBT, which greatly increases the complexity of the system and loss, but also reduces the reliability of the system.
In the mid-1990s, ABB researchers made the technological leap from GTO HD-GT0 by optimizing the GTO drive unit and device shell design, and adopting integrated gate and other technologies to greatly reduce the requirements of GTO drive circuits. However, the on-state loss of HD-GTO is relatively large, so the researchers draw on various loss reduction technologies accumulated in the development of IGBT to medium and high voltage. The structure of HD-GTO is optimized, and it is named IGCT, integrated gate commutator thyristor, together with its integrated hard drive gated unit.
In summary, IGCT has both the on-off characteristics of GTO and the switching characteristics of IGBT. It is characterized by high current, high voltage, high switching frequency, high reliability, compact structure and low loss, and its performance is obviously better than that of GTO and IGBT devices widely used at present.
IGCT is mainly composed of the main switching device GTC and its corresponding integrated gate drive unit. GTC is evolved from GTO, introducing buffer layer, anode transparent emitter and inverse conduction structure. The profile structure of its core device GTC is shown in Figure 1.
The traditional concept of a non-penetrating type is to form an anode by direct diffusion over a thick N-base region. When non-through-PN junction is blocked, the electric field distribution is triangular, as shown in Fig.1. It can be seen from Figure 2 that the total blocking voltage of the device is the integral of the electric field along the thickness of the silicon wafer. Therefore, the higher the blocking voltage is required, the thicker the silicon wafer will be, while the maximum strength of the electric field applied to the material remains unchanged. In this way, the on-off loss and switching loss of the device will increase correspondingly.
