High Frequency Noise in Dar Impatt Diode Considering Unequal Ionization Rates and Drift Velocities of Electrons and Holes

Abstract

A study on the generalized high frequency noise properties of DAR Impatt diode has been carried out for Si and GaAs considering realistic values of ionization rates and saturated drift velocities for electrons and holes. From the study, it has been found that at the same biasing current level, the negative conductance and noise figure of DAR Impatt are comparable with those of its equivalent SDR Impatt. However, because of space-charge cancellation, the DAR Impatt will withstand higher biasing current density compared to the conventional SDR and DDR Impatts, where there is considerable space charge effect. From the results of different DAR Impatts having same avalanche layer widths but different depletion layer width, it is observed that the noise figure is less and negative conductance peak higher for the narrower structure. Thus the DAR Impatt with narrower structure may prove to be a useful microwave source in the mm-wave range. The effect of diffusion in the drift zone is found to be negligible on the device performance, except at certain frequencies where there is some degradation owing to diffusion induced reduction of negative conductance. From comparison of results, it is also observed that for identical conditions of operation and for same operating range of frequency, the GaAs DAR Impatt has higher negative conductance and lower noise figure relative to its Si counterpart.