InP High Electron Mobility Transistors with InAs-based Channels for High Frequency and Low Noise Applications

Indium phosphide based high electron mobility transistors (InP HEMTs) offer outstanding channel transport properties required for high-speed, high-gain and low-noise performance. They are the key components of low-noise receivers, and their field of application includes telecommunications, imaging, spectroscopy and even quantum computing. For years they have been considered as the best option for low-noise amplifiers, where the most critical metrics depend not only on speed and gain but also on noise performance both at room and cryogenic temperatures. Although gate length miniaturization and channel composition optimization enable record cutoff frequencies, noise performance shows a different trend. Further developments in noise of sub-100 nm devices are not achieved due to their increased drain noise. Additionally, vertical device scaling entails higher gate leakage, thus degrading the noise performance even further. This work covers the epitaxial layer optimization of InP HEMTs with InAs channel insets using bandgap engineering and varying the device geometry. Composite channel structures with narrow and wide bandgap materials were implemented to reduce the effects of impact ionization and lower the gate leakage currents while keeping an excellent RF performance. Devices were characterized by extensive DC and RF measurements at room and cryogenic temperatures. To correlate the device results to its circuit behavior, small-signal device modeling was performed for various epitaxial structures. The used small-signal model accounts for the effects of impact ionization and presents excellent agreement between measured and simulated data. Noise performance at room temperature was also investigated by means of noise parameters measurements. Based on the figures-of-merits for different device geometries and layer stacks, further developments in the fabrication technology could be identified, leading to progress in noise performance