Cryogenic GaN LNA with integrated NbN superconducting mixers: compact THz detectors for future radioastronomy receivers

Research Project, 2019 – 2022

The overall purpose of this proposal is to demonstrate a compact, single chip, THz detector based on the unique performance combination, which the direct integration of NbN superconducting bolometer to a GaN Low-Noise Amplifier (LNA) would provide at cryogenic temperatures. Such detector chips would provide the most suited, compact and reliable solution to meet the needs of future multi-pixel THz receiver for radio astronomy.Practically, the project implies a technological merging of the proven epitaxial NbN thin film technology using GaN buffer layers developed the well-established GaN MMIC process developed by the apllicants into a final platform, where GaN is grown on Si substrates, enabling the final integration into a waveguide circuit demonstrator.The specific scientific goals for the different work packages and project are:Doubling of the IF bandwidth for a NbN mixer compared to today’s state-of-the-art (~8 GHz instead of 3-4 GHz), due to the epitaxial NbN material’s superior performance and better phonon transparency at the NbN/GaN interface.Demonstration of high gain and low-noise performance comparable to III-V technologies for GaN-based LNAs, by an aggressive downscaling of the GaN HEMTs and employing advanced solutions for reducing resistances, e.g, regrown contacts. This strategy also reduces the LNA power consumption, to prevent local heating, hence breaking of superconductivity of the NbN mixer.Demonstration of an integrated NbN and GaN integrated detector chip