Tunable two-dimensional plasmon resonances in an InGaAs/InP high electron mobility transistor

Voltage-tunable plasmon resonances in the two-dimensional electron gas 2DEG of a high electron mobility transistor HEMT fabricated from the InGaAs/InP materials system are reported. The device was fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography and a semitransparent gate contact that consisted of a 0.5 m period transmission grating formed by electron-beam lithography. Narrow-band resonant absorption of terahertz radiation was observed in transmission in the frequency range of 10–50 cm−1. The resonance frequency depends on the gate-tuned sheet charge density of the 2DEG. The observed separation of resonance fundamental from its harmonics and their shift with gate bias are compared with theory. © 2009 American Institute of Physics. DOI: 10.1063/1.3129319