On the relation between rf noise and subthreshold swing in InP HEMTs for cryogenic LNAs

4 - 8 GHz low-noise amplifiers (LNAs) based on InP high electron mobility transistors (InP HEMTs) with different spacer thickness in the InAlAs-InGaAs heterostructure were fabricated and characterized at 5 K. A variation in the lowest average noise temperature of the LNA was observed with spacer thickness. We here report that the subthreshold swing (SS) at 5 K for the HEMT exhibited similar dependence with spacer thickness as the lowest average noise temperature of the LNA. This suggests that low-temperature characterization of SS for the HEMT can be used as a rapid assessment of anticipated noise performance in the cryogenic HEMT LNA.

Automated summary

This study fabricates and characterizes 4-8 GHz low-noise amplifiers (LNAs) based on InP HEMTs, with different spacer thicknesses in the InAlAs-InGaAs heterostructure, at 5 K. The results show that the lowest average noise temperature of the LNA varies with the spacer thickness. Additionally, the subthreshold swing (SS) of the HEMT at 5 K exhibits a similar dependence on the spacer thickness as the lowest average noise temperature of the LNA. This suggests that the low-temperature characterization of SS in the HEMT can be used as a quick assessment of the anticipated noise performance in the cryogenic HEMT LNA.