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The conversion efficiency for planar Al0:7GaAs/ GaAs heterostructure barrier varactor triplers is shown to be reduced from a theoretical efficiency of 10% to 3% due to selfheating. The reduction is in accordance with measurements on planar Al0:7GaAs/GaAs heterostructure barrier varactor (HBV) triplers to 261 GHz at room temperature and with low temperature tripler measurements to 255 GHz. The delivered maximum output power at 261 GHz is 2.0 mW. Future HBV designs should carefully consider and reduce the device thermal resistance and parasitic series resistance. Optimization of the RF circuit for a 10-m diameter device yielded a delivered output power of 3.6 mW (2.5% conversion efficiency) at 234 GHz.

A technique has been developed which allows the fabrication of channels within the body of multiple layers of negative resist. Previously this was only possible in the positive resist system but with the transfer to negative resist, higher and more clearly defined channels are now possible. Thick negative resists are also easier to process than their positive counterparts, allowing multiple crossing channels. The physical structure of a full height W-band waveguide with an integrated E-plane filter has been fabricated with this technique. The fabrication procedure presented in this paper is quick, reproducible and easily implemented using standard photolithography equipment.

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