Ultra-low noise characteristics of millimeter-wave high electron mobility transistors

Room-temperature noise performance of high-electron-mobility transistors (HEMTs) has been studied by correlating the microwave/millimeter-wave noise figure with lower frequency model parameters. By comparing devices fabricated from various molecular-beam epitaxially grown wafers, it is found that devices with high transconductance at low drain current generally exhibit superior noise performance. In particular, an optimal noise figure of 1.8 dB has been obtained at 60 GHz with 6.4-dB associated gain for devices from the best wafer. The low thermal noise coefficient ( theta <1) measured for these devices indicates a high carrier saturation velocity and negligible hot-electron effect.<>