Terahertz Detection with 2D Plasmons in Grating Gated High Electron Mobility Transistor

The terahertz band of the electromagnetic spectrum has many promising applications such as imaging for security or medical purposes, far infrared spectroscopy, and the study of protein dynamics. However, the terahertz part of the electromagnetic spectrum is not being used to its full advantage due to the technological difficulties in developing tunable coherent sources and sensitive tunable narrowband detectors. Our project explores a special grating gated, GaAs/AlGaAs, high electron mobility transistor (HEMT) as tunable terahertz detectors. In this device, the electric field of the incident terahertz radiation resonantly excites the 2D plasmons within the device. The periodic grating gate defines the wavevector of the 2D plasmon and the voltage of the grating gate controls the electron density. In this situation, the gate voltage can control the 2D plasmon frequency. In addition to the grating gate, there is a small separate gate that operates as a bolometric sensor when biased beyond pinch-off. Accordingly, the terahertz radiation is sensed by this bolometric sensor as a change in impedance of the channel due to the increased temperature of the resonantly excited 2D electron gas. Currently, our devices are operated at cryogenic temperatures but the ultimate goal of this research is to develop a detector that operates at higher temperatures while retaining the tunable narrowband response.