Characteristics of dry-etched GaAs p–n junctions grown by mombe

We demonstrate that MOMBE using all gas-sources (AsH₃, TMGa, TEGa and TESn) is capable of producing p-n junctions suitable for high performance GaAs/AlGaAs HBTs. Both Sn and C profiles measured by SIMS showed sharp turn-on and turn-off of the respective dopants, and n-on-p and p-on-n diodes had 4 decade linear regions with ideality factors of 1.55. The absence of cross-contamination of C in the n-GaAs and Sn in the p-GaAs produced diodes with improved characteristics over those grown with solid As reported earlier. HBTs fabricated on our MOMBE grown layers exhibit unilateral current gains and maximum frequencies of oscillation above 60 GHz. To simulate the ion bombardment during plasma etching with either CCl₂F₂/O₂ or CH₄/H₂ mixtures, we exposed our samples to 1 mTorr O₂ or H₂ plasmas for periods of 1–20 min with DC biases of −25 to −400V on the cathode. For O₂ ion bombardment the collector resistance showed only minor (≤10%) increases for biases up to −200 V. The base resistance displayed only a minor increase over the pre-exposure value, even for O⁺ energies of 375 eV, due to the very high doping in the base. More significant increases in both R_c and R_b were observed for H⁺ ion bombardment due to hydrogen passivation effects.