Beam-Lead plated heat sink GaAs IMPATT: Part I—Performance

GaAs IMPATT devices are currently being developed for use as high-power microwave oscillators. Since low thermal impedance is required for dissipation of high input powers, this device is usually fabricated by thermal compression bonding to a diamond heat sink or a multimesa plated heat sink. This paper discusses the development of 4-mesa beam-leaded plated heat sink (BLPHS) C- and X-band GaAs IMPATT diodes. A description of the fabrication procedures is given, whereby the beam-lead interconnects are formed as part of the wafer fabrication procedure. Diodes tested at 5 GHz give up to 7.3 W of output power at 13.5- percent efficiency at a junction temperature of approximately 210°C. X-band diodes, although the data is more limited, show efficiencies up to 16.5 percent (2.2 W) for fiat profile diodes, and up to 20.8 percent for lo-hi-lo profile diodes. BLPHS diodes, therefore, are limited in their efficiency by the epitaxial material´s doping profile. Accelerated stress aging data taken to date on BLPHS units show them to have an estimated mean time to failure greater than 2 × 10⁶h at 200°C, which is comparable to thermal compression bonded to diamond units.