Switching characteristics of the initially unbiased four-layer silicon device operating in impact-ionization mode

The switching characteristics of layered silicon device with p+npn+ structure under zero bias voltage were investigated in this paper. A long base device with 10 mm diameters and 4.3 kV operating voltage was used in the experiments. According to the significant difference in the trigger current, the trigger types are divided into two modes, named strong mode and weak mode respectively. The experiment results show that, in both modes, the device can be switched within 200 ps followed by a residual voltage lower than 100 V, and the delay time of switching increases with the decrease of voltage rise rate dU/dt. In each mode, the dependences of the switching time and residual voltage on the dU/dt are similar to the state of reversely biased device. However, comparing the two modes, due to the earlier collision between the ionization front and extraction front, and subsequently the longer quasi-uniform breakdown region in the n-base, the switching time and residual voltage may be larger than those of the weak mode, although the dU/dt is higher in the strong mode. The results show that, the switching performance of the device under test does not depend monotonously on the dU/dt, which implies a moderate dU/dt may be favorable to the ultra-fast switching for a long base and low bias four-layer device.