ION-IMPLANTED HYPERABRUPT VARACTOR DIODES FOR GAAS MMICS

The design, fabrication, and characterization of monolithically compatible varactor GaAs diodes are described. An all ion-implantation process was used to fabricate hyperabrupt varactor diode with large (>10:1) tuning ratios, and high-energy (4- and 6-MeV) implantation was employed to form a buried n+ layer below the active portion of the device. Additional implantations were performed to provide surface contact to the buried layer and to form the hyperabrupt capacitor profile. Nearly ideal Schottky barriers with an integral high-resistivity guard ring for depletion of the hyperabrupt profile were fabricated. These barriers show an ideality factor of 1.0, low reverse leakage current, and high reverse avalanche breakdown voltage (>30V). The varactor diodes were characterized at frequencies between 2 and 10 GHz. Data on measured performance in this frequency range, and correlation with the device structure, are presented, and details of the device design, ion-implantation experimental data, and diode electrical characterization are discussed.