Device Design And Optimization Of A Novel Insulated-Gate Photoconductive Switch

Photoconductive semiconductor switches(PCSSs)have attracted much attention in power devices and ultra-fast devices because of high pressure,high power,fast response and no electromagnetic interference.PCSSs have broad prospects in the field of high power ultra-wideband pulse generation and ultra-fast electronics,and have the potential to become a core part of pulse generation system.In this paper,the current status of the development of PCSSs domestic and overseas and the problems existing in practical process are analyzed.After analyzing and comparing the physical properties of Si(the first generation semiconductor)and GaAs(the second generation semiconductor),semi-insulating GaN:Fe is selected as the substrate material of the device and a 10-kV-voltage GaN PCSS triggered with a 532-nm-wavelength laser is designed.At present,the breakdown field strengths of GaN PCSSs with traditional structures are much smaller than the theoretical value corresponding to the intrinsic forbidden band width.After the relevant reasons are analyzed,a structure of vertical-double-diffusion insulated-gate PCSS(VDIG-PCSS)is first proposed.A vertical-double-diffusion field-effect-transistor array is added to the traditional PCSSs,which means a reverse pn junction controlled with the gate voltage is introduced.It is not only reduces leakage current under high DC bias voltage by utilizing expulsion effect of space charge region to the carriers in semi-insulating GaN:Fe substrate,but also dynamically transfers voltage from electric-triggered area to laser-triggered area waiting for triggering controlled with the gate voltage signal.The new structure proposed is modeled and simulated using Silvaco.Next,the static characteristics,the dynamic characteristics and the photocurrent output characteristics are analyzed.The simulation results show that the VDIG-PCSS can not only reduce the leakage current effectively,but also slightly improve the efficiency of laser energy.Finally,an external characteristic testing system with the generators of the gate voltage and the laser pulses is built,and the resistivity and breakdown field strength of the semi-insulatng GaN:Fe are measured...