High-efficiency transferred substrate GaAs varactor multipliers for the terahertz spectrum

We report here the performance improvement of frequency doublers using substrate transfer technique, the method by which the diodes/MMIC circuits made on GaAs substrate have been subsequently transferred on to a host substrate like Quartz and Aluminium Nitride. These host substrates have low loss and high thermal conductivity at mm-wave and sub millimeter wave frequencies. The substrate transfer technique on RAL doubler circuits designed at 160 GHz gives a conversion efficiency ~ 30% and 3 dB BW >15%, which is a significant performance improvement compared to the same diodes on GaAs substrate. The efficiency and bandwidth at a constant input power has been studied using doubler diodes of different anode areas and the results are presented in this paper. The measured data is compared to simulations, and the test results agree closely to predictions.