Characterization of GaAs Schottky-read IMPATT diodes

In a recent paper, the oscillator performance of GaAs Schottky-Read diodes of the type metal - n1n2n⁺was given (4). Efficiencies as high as 26% were observed at X-band for a ratio n1/n2≈ 25. The tuning characteristics of these diodes differ considerably from conventional IMPATTS which have uniform doping profiles. In addition, the Schottky-Read diodes have proved to be difficult to use in microstrip amplifier circuits, particularly at high rf input levels. Small and large signal admittance measurements were made at frequencies from 4 to 12 GHz for different dc current levels on a number of diodes with differing profiles, I-V characteristics, and oscillator performance. The results were compared with those obtained for conventional IMPATTS. In addition, the effect of structural variations on breakdown voltage and depletion depth were calculated.