Plasma wave interactions in the microwave to THz range between carriers in a semiconductor 2DEG and interdigital slow waves

Traveling wave interactions between the plasma wave in a two-dimensional electron gas (2DEG) in the AlGaAs/GaAs high electron mobility transistor (HEMT) structure and the electromagnetic space harmonic slow waves produced by interdigital metal electrodes were investigated both theoretically and experimentally. By means of a TM mode analysis, a general expression for the ω- and k-dependent effective permittivity of the 2DEG plasma was derived. The two-terminal admittance was calculated by a Green’s function method from the microwave to the THz wave region. Occurrences of negative admittance were predicted, and its peak values increased with frequency to a very large value in the THz region due to the reduction in the number of collisions per cycle. Preliminary admittance measurements at microwave frequencies showed good agreement with calculations, confirming the existence of plasma wave interactions.