COMPUTER STUDY OF OPTIMUM MILLIMETER-WAVE CONDUCTANCE OF GAAS AND SI DOUBLE DRIFT IMPATT DIODES FOR FLAT AND LOW-HIGH-LOW STRUCTURES

A comparative study of de and small signal characteristics of GaAs and Si double drift (flat and low-high-low) structures operating in the 2 8-56 GHz frequency band has been carried out keeping both the total de pletion layer width as well as the de bias current constant. The resul ts show that the upward shift in operating frequency due to incorporat ion of impurity bumps is more in case of GaAs diodes than for Si diode s. The optimum value of high frequency negative conductance is larger for Si DDR compared to GaAs. Also the increase in magnitude of the neg ative conductance is larger for Si DDR compared to its GaAs counterpar t when the structure changes from flat to low-high-low (LHL).