Variable mechanism of electrical impedance for MCT high voltage switch under synergetic action of the mechanical and electric loads

Abstract

To study the electromechanical coupling effect of Metal Oxide Semiconductor Controlled Thyristor (MCT) high voltage switch under the synergistic action of mechanical load and strong voltage in the actual use of penetrating hard targets and launching, the universal testing machine was used to simulate the overload environment. The rising edge time, falling time and impedance changes in the conduction path of MCT under different stress–strain were tested, respectively. Experimental results showed that the rise time of MCT decreased from 0.08 ms to 0.03 ms when the uniaxial compressive stress increased from 1.20 MPa to 7.3 MPa, and the rising edge time after unloading was 0.04 ms. The falling time had no obvious change with the increase of stress. The total resistance in the path decreased from 833.30 Ω to 564.22 Ω with the increase of strain. The stress–strain of each part of MCT under different uniaxial compressive stress was collected by COMSOL Multiphysics finite element software. Based on the Schrödinger equation, the potential energy operator was established. By introducing the strain Hamiltonian H ε,ν , the E(k)-k model near the minimum value of the conduction band of Si was established by using the k·p perturbation method. Combined with the physical field interface of Schrödinger equation in COMSOL Multiphysics, the valence band structure of Si material under uniaxial strain was studied on the basis of strain Hamiltonian perturbation. The results showed that the 6-degree degenerate valley (Δ6) in the conduction band was split into a 2-degree degenerate valley (Δ2) and a 4-degree degenerate valley (Δ4) due to the stress effect. The strain caused more electrons to occupy the lower Δ4 energy valley, resulting in a decrease in the effective mass of the total conductivity. Therefore, the electron mobility of Si was increased under uniaxial strain. The uniaxial compressive stress could more effectively reduce the curvature radius of valence band top, the effective mass of carriers and the interband scattering between light and heavy hole bands, which was beneficial to improve the hole mobility.