Investigation of Drain Noise in Cryogenic InP High Electron Mobility Transistors Using On-wafer S-parameter and Microwave Noise Characterization

We report the on-wafer characterization of S-parameters and microwave noise (T50) of discrete InP HEMTs over a range of physical temperatures, 40 K – 300 K. From these data, we extract a small-signal model and the drain noise temperature (Td) at each bias and temperature. We find that T50 exhibits a temperature dependence that is incompatible with a fixed Td. In contrast, explaining the noise measurements requires Td to change from ~2500 K at room temperature (RT) to ~400 K at cryogenic temperatures. This trend is consistent with the predictions of a theory of drain noise based on real-space transfer of electrons from the channel to the barrier [5].