A COMPARATIVE STUDY OF Si- AND GaAs-BASED DEVICES FOR REPETITIVE# HIGH-ENERGY, PULSED SWITCHING APPLICATIONS

A study is performed to assess Si and GaAs as materials for realization of repetitive, highenergy, pulsed switches in applications where the switching parameters are blocking voltages (V B ) exceeding 1 kV in the off state and conduction currents (I F) in excess of 500 A in the on state, the current risetime being less than 1 ps and the pulse length being longer than 50 ns. Theoretical and technological limitations associated with the switching characteristics of Si- and GaAs-based majority carrier (unipolar) and minority carrier (bipolar) devices in the low-field. high-mobility, and high-field velocity saturation regimes are analyzed and discussed. It is concluded that for medium power applications (V B I F <300 kW, V B >1 kV), majority carrier devices are best suited for fast switching processes in the low-field, low current density (J<100 A/cm 2 ) regime. Under such conditions, the high drift mobility of GaAs allows for realization of field-effect devices exhibiting fast switching speeds and low. on-state conduction losses. For pulsed switching in the high-power regime (300 KW1 kV), bipolar structures exhibit the most desirable characteristics, while compared to their Si counterparts, the on-state conduction losses of GaAa-based devices are extremely high. These considerations are extended to stacked Si bipolar devices and semi-insulating GaAs photoconductive switches for ultrahigh-power (>30 MW) switching applications.