GaAs-modules for power generation at W-band frequencies

A novel technique for the encapsulation of GaAs transit-time devices is applied for power generation at W-band frequencies. The fabrication process leads to excellent reproducibility of the mounting parasitics und easy device handling. The active devices are realized with an IMPATT-diode structure for use on diamond heat-sinks. Maximum output power of 165 mWatt at 87 GHz and 80 mWatt at 98 GHz has been obtained. The highest oscillation frequency is 110 GHz. For the development of mm-wave oscillators the impedance matching of the active rf-semiconductor device and resonator structure is the most important task. The problems arising from this matching increase with elevated frequencies as the diode encapsulation determines more and more the coupling between active device and resonant circuit. Generally, the parasitic elements due to encapsulation must be minimized as much as possible. Until now, for mm-wave frequencies the active devices have been encapsulated with the help of quarz stand-offs or rings and gold bond ribbons (Weller [1] Wenger [2], Eisele and Haddad [3]). As a fact of this relatively delicate procedure often large deviations in the values of the parasitics may result. On the other hand, it has been shown by several authors in the field of MMIC-technique for mm-wave oscillators, that exactly controlled fabrication processes can lead to high reproducibility up to W-band frequencies (see for example: Bayraktaroglu [4], Bogner and Freyer [5], Lbuy et al [6]).