Cryogenic high frequency operation of tunneling hot-electron transfer amplifiers

In this paper, we describe the cryogenic high speed operation of fixed and composition bandgap collector THETA devices in which the In composition within the 40 nm base has been varied from 53% to 62%. The cryogenic on-wafer measurement system at the Georgia Institute of Technology has been used to collect S-parameters at 18 K and 300 K. Initial results indicate that, at a constant bias, f_T increases by almost a factor of 2, from 15 GHz to 30 GHz, as the temperature is reduced from 300 K to 18 K primarily as the result of increased current gain. Detailed small-signal model development is presented to help estimate performance of scaled THETA structures at room temperature