Double-drift IMPATT diodes near 100 GHz

This paper reports the highest power (frequency)²IMPATTS produced to date. A CW output power of 380 mW has been achieved at 92 GHz with an efficiency of 12.5 percent. An all-implanted double-drift n⁺-n-p-p⁺silicon structure was fabricated, using a lightly doped epitaxial layer as the starting material. The newly made structure uses a more shallow n⁺contact than previous diodes, and therefore has more equal drift spaces. Small-signal admittance calculations show lower susceptance per unit area in the newly made structure. The shallow contact has allowed the study of unequal dopings in the n- and p-drift spaces. Unequal dopings up to 50 percent can be tolerated with less than 20 percent variation in measured efficiency and output power. Both admittance and breakdown voltage calculations based upon experimentally determined doping profiles and independently measured ionization coefficients were found to be in good agreement with experiment. The doping profiles on both sides of the depletion region were determined by analysis. The testing of both the old and new structures has been carried out in a microwave circuit having improved mechanical tuning accuracy due to the introduction of a newly designed tuning plunger.