InP High Electron Mobility Transistor Design for Cryogenic Low Noise Amplifiers
The InGaAs/InAlAs/InP high electron mobility transistor (InP HEMT) is the superior technology for the most demanding low-noise and high-speed microwave and millimeter-wave applications, in particular in radio astronomy and deep-space communication. InP HEMT has enabled cryogenic low noise amplifier (LNA) designs with noise temperatures about ten times the quantum noise limit from sub GHz up to 120 GHz. In this thesis, design techniques of 100 nm gate length InP HEMTs for state-of-the-art cryogenic LNAs are reported. Detailed DC, RF and noise analysis for the InP HEMTs at 300 K and 5 K are presented. The thesis is divided into two parts.
The first part of the work reports on the optimization of 100nm gate length InP HEMT technology for cryogenic LNA applications at microwave frequencies. By scaling the gate length and barrier thickness combined with reduction of source and gate resistances, advances in cryogenic noise performance for wideband monolithic microwave integrated circuit (MMIC) LNA were demonstrated in the frequency range 0.3-28 GHz. At 4 K, the minimum noise temperature was 2.2 K and 4.8 K for a 0.3-14 GHz and 16-28 GHz LNA, respectively. The cryogenic MMIC LNAs demonstrated state-of-the-art noise performance.
In the second part, cryogenic stability of two-finger InP HEMTs is investigated. The InP HEMTs exhibited anomalous behavior in terms of jumps in drain current, sharp peaks in transconductance, and decreased gain under cryogenic operation. Three different design techniques for two-finger HEMTs were tested to mitigate the anomalous instabilities associated with cryogenic operation. By either adding a source air-bridge, connecting the back end of gates or increasing the gate resistance, stable device operation was demonstrated for each case. Successful stabilization was confirmed both on device and circuit level by cryogenic measurements. A three-stage 24-40 GHz and a four-stage 28-52 GHz MMIC LNA based on the source air-bridge design technique for the two-finger InP HEMTs were demonstrated at 5.5K. The minimum noise temperature was 7 K and 6.7 K in the 24-40 GHz and 28-52 GHz LNA, respectively. Both designs demonstrated the lowest noise temperature reported so far for cryogenic MMIC LNAs for these frequency bands.