Thermal Characterization of Substrate Options for High-Power THz Multipliers over a Broad Temperature Range

This paper presents thermal characterization results for three high-power THz Schottky frequency multipliers in the temperature range of 20-380 K. All measured multipliers have different substrates: a 5-μm-thick GaAs membrane, a 40-μm-thick GaAs substrate, and a 5-μm-thick GaAs membrane glued to a 20-μm-thick CVD diamond substrate with polymer bonding agent. The thermal characterization results include such parameters as the maximum average junction temperature of the anodes, device total thermal resistance, and device cooling (or heating) times. The results enable designers to better optimize their devices for the maximum power level and temperature range and system engineers to better predict the overall performance of the system in an environment, where the ambient conditions might change. For example, from the thermal resistance point of view the GaAs membrane on diamond substrate clearly outperforms the device on GaAs membrane alone at room temperature or above. However, perhaps surprisingly, at temperatures below 125 K, the GaAs membrane is on par, or even has lower thermal resistance than the membrane on diamond.