MODELING AND OPTIMIZATION OF GALLIUM-ARSENIC SCHOTTKY BARRIER MIXER DIODES (SUBMILLIMETER)

In recent years, technological advances have made possible the design and fabrication of cryogenically cooled heterodyne receivers with operating frequencies as high as 350 GHz, and room temperature receivers operating as high as 2.5 THz. These receivers rely on the excellent performance of the current state-of-the-art GaAs Schottky barrier mixer diodes. The reduced operating temperature and reduced diameter of these high frequency diodes, while improving performance, have necessitated a review of the models which are used to predict their electrical behavior.;Models which describe the performance of mixers incorporating the Schottky diode are investigated. In particular the intrinsic conversion loss model of McColl is re-analyzed in light of the more complete model of the Schottky diodes developed herein. This analysis removes the discrepancies between the theoretical predictions of this model and experimental data.;More precise models of conversion loss and the mixer noise temperature 10,11 are investigated and extended to include our model of the high field noise. These models are then used to investigate the performance of the Schottky diodes, and several insights into the diode performance are developed. The importance of the R(,s)-C(,jo) product to the mixer performance is supported by experimental results. The most promising method of improving the performance of submillimeter wavelength mixer diodes is shown to be reduction of the R(,s)-C(,jo) product.;In this research the current-voltage characteristics of the cryogenically cooled mixer diodes are shown to be governed by hot electron effects. These effects are seen to significantly degrade the noise performance of the diodes. The nature of the capacitance-voltage characteristic at high forward bias values is discussed, and its effect on the high frequency performance of the diodes is analyzed. The DC biased equivalent noise temperature of the diodes is discussed and current models are extended to include the diode junction capacitance and the high field noise. The high field noise is shown to be caused by hot electron effects in typical high frequency diodes.