Millimeter wave emission from GaN high electron mobility transistor

We report on millimeter wave electromagnetic radiation from a GaN high electron mobility transistor with the gate length of 1.5 mum at 8 K. The emission takes place at gate and drain voltages in the linear regime of operation but close to the saturation voltage with the principal emission peak at approximately 75 GHz, which is much higher than the device cut-off frequency. An explanation of this effect involves the "shallow water" plasma wave instability, with the frequency of the plasma waves decreased by the ungated regions of the device. (C) 2004 American Institute of Physics.