Novel GaN-Based HFET Sources and Amplifiers for Millimeter-Wave Applications

We propose to develop GaN HFET based sources with enhanced RF operation characteristics at millimeter wave frequencies and beyond by utilizing combination of our novel plasma wave approach and newly observed electron-transit-time effects. Electron-transit-time effects in the saturation regime of HFETs might lead to the plasma wave instability which decrease the plasma wave decay and, hence, emission of radiation at millimeter and sub-THz frequencies. Our proposed solution is based on the "plasma wave approach" which was developed by Dyakonov and Shur in early 90s and recently confirmed by several experimental observations. We have demonstrated that, in many cases, the two dimensional electrons in the FET channel may be described by hydrodynamic equations which coincide with those for shallow water, plasma waves in the FET channel being similar to shallow water waves. We also showed that in a short enough device, an instability should occur at a relatively small direct current because of spontaneous plasma wave generation. This provides a new mechanism for the emission of tunable millimeter wave radiation.