# High-efficiency spontaneous terahertz emission from electrically-excited plasmons in AlGaN/GaN two-dimensional electron gas

## TL;DR

This paper demonstrates tunable spontaneous terahertz emission from AlGaN/GaN 2DEG with variable efficiency, showing potential for high-power, room-temperature solid-state terahertz sources through electrical excitation of plasmons.

## Contribution

It reports a novel high-efficiency, tunable terahertz emission from AlGaN/GaN 2DEG using electrical excitation, achieving efficiencies up to 10% and demonstrating potential for practical terahertz sources.

## Key findings

- Tunable terahertz emission from 0.3 to 2.5 THz.
- Wall-plug efficiency up to 10%.
- Detectable emission power below 15 nW.

## Abstract

The advance of terahertz science and technology yet lays wait for the breakthrough in high-efficiency and high-power solid-state terahertz sources applicable at room temperature. Plasmon in two-dimensional electron gas (2DEG) has long been pursued as a type of promising active medium for terahertz emitters. However, a high wall-plug efficiency sufficient for high-power operation has not been achieved. Here we report spontaneous terahertz emission tunable in a frequency range from 0.3 to 2.5 THz through electrical excitation of plasmon or plasmon-polariton modes in a grating-gate coupled AlGaN/GaN 2DEG at 7 K. A wall-plug efficiency ranging from $10^{-6}$ to $10^{-1}$ is found by tuning the energy (4.5 eV to 0.5 eV) of tunneling electrons between the grating gates and the 2DEG. The total emission power, albeit below 15 nW, is already detectable by using a direct terahertz field-effect transistor detector based on the same type of 2DEG. The findings indicate that both high-efficiency and high-power terahertz plasmon-polariton emission could be obtained by a proper injection of tunneling electrons with low energy and high current density.