InP High Electron Mobility Transistors for Cryogenic Low-Noise and Low-Power Amplifiers
Sammanfattning: The InAlAs/InGaAs/InP high-electron mobility transistor (InP HEMT) is the preferred low-noise device in cryogenic low-noise amplifiers (LNAs) operating at 5-15 K. Such LNAs are utilized in microwave and millimeter-wave detection in radio astronomy. In order to further reduce the noise level, a deeper understanding of the InP HEMT under cryogenic low-noise operation is necessary. In addition, InP HEMTs with very low dc power dissipation have recently become of interest due to power constraints when scaling quantum computing systems with large number of cryogenic LNAs. This thesis presents progress in InP HEMT technology for cryogenic LNAs. Three areas are addressed: device scaling, dc power optimization, and electrical stability at cryogenic temperature. The InP HEMT optimization are discussed in terms of the epitaxial layer design, fabrication, dc, rf, and noise characteristics. A 100 nm gate-length InP HEMT technology was developed by scaling of the barrier thickness. Despite increased gate leakage current, state-of-the-art cryogenic noise performance for a wide-band monolithic microwave integrated circuit (MMIC) LNAs was demonstrated with average noise temperature of 3.5 K and 6.3 K for the 0.3-14 GHz and 16-28 GHz designs, respectively. The impact of barrier thickness and channel composition on the cryogenic noise temperature and dc power dissipation of the InP HEMT LNAs was studied. Through the barrier scaling, the HEMT achieved an improvement of transconductance to drain current ratio at low drain voltages, which enabled a reduction of the power dissipation to 112 uW with an average noise temperature of 4.1 K in a 4-8 GHz InP HEMT LNA. From a comparative study of In0.65Ga0.35As and In0.8Ga0.2As channels, the InP HEMT with lower indium channel content resulted in superior cryogenic noise performance. The cryogenic stability of two-finger InP HEMTs was investigated. The InP HEMTs exhibited anomalous electrical behavior such as jumps in drain current and sharp peaks in transconductance. Three different design techniques were shown to mitigate the electrical instabilities associated with cryogenic operation. A cryogenic 24–40 GHz and a 28–52 GHz MMIC LNA based on the source air-bridge design technique for the two-finger InP HEMTs were demonstrated. The average noise temperature was 10.6 K and 10 K in the 24-40 GHz and 28-52 GHz LNAs, respectively. Both LNA designs demonstrated the lowest noise temperature reported so far for cryogenic MMIC LNAs for these frequency bands.
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