Reduction of Noise Temperature in Cryogenic InP HEMT Low Noise Amplifiers with Increased Spacer Thickness in InAlAs-InGaAs-InP Heterostructures

Other conference contribution, 2021

The impact of InP HEMT spacer thickness on cryogenic performance in low noise amplifiers (LNAs) has been investigated. 100 nm gate-length InP HEMTs based on InAlAs-InGaAs-InP heterostructures with different spacer thickness (1 nm, 3 nm and 5 nm) were fabricated. The Hall measurements, simulated band structures and dc characteristics of InP HEMTs were compared for all the three different epitaxial structures at 5 K. The noise performance of the InP HEMT was studied using a three-stage 4–8 GHz hybrid LNA at 5 K. All LNAs yielded an average gain above 30 dB across the whole band. When biased for optimal low noise operation, the LNA with 5 nm spacer thickness InP HEMTs achieved an average noise temperature of 1.3 K. The LNAs with spacer thickness of 1 nm and 3 nm InP HEMTs exhibited a higher average noise temperature of 1.9 K and 1.7 K, respectively. The reduction in LNA noise temperature with increased spacer thickness was observed to correlate with a strongly enhanced electron mobility in the InP HEMT structure at 5 K.