Terahertz Radiation from High Electron Mobility Avalanche Transit Time Sources Prospective for Biomedical Spectroscopy

Abstract

A Schottky barrier high-electron-mobility avalanche transit time (HEM-ATT) structure is proposed for terahertz (THz) wave generation. The structure is laterally oriented and based on AlGaN/GaN two-dimensional electron gas (2-DEG). Trenches are introduced at different positions of the top AlGaN barrier layer for realizing different sheet carrier density profiles at the 2-DEG channel; the resulting devices are equivalent to high–low, low–high and low-high–low quasi-Read structures. The DC, large-signal and noise simulations of the HEM-ATTs were carried out using the Silvaco ATLAS platform, non-sinusoidal-voltage-excited large-signal and double-iterative field-maximum small-signal simulation models, respectively. The breakdown voltages of the devices estimated via simulation were validated by using experimental measurements; they were found to be around 17–18 V. Under large-signal conditions, the series resistance of the device is estimated to be around 20 Ω. The large-signal simulation shows that the HEM-ATT source is capable of delivering nearly 300 mW of continuous-wave peak power with 11% conversion efficiency at 1.0 THz, which is a significant improvement over the achievable THz power output and efficiency from the conventional vertical GaN double-drift region (DDR) IMPATT THz source. The noise performance of the THz source was found to be significantly improved by using the quasi-Read HEM-ATT structures compared to the conventional vertical Schottky barrier IMPATT structure. These devices are compatible with the state-of-the-art medium-scale semiconductor device fabrication processes, with scope for further miniaturization, and may have significant potential for application in compact biomedical spectroscopy systems as THz solid-state sources.

On-Chip Modification of Titanium Electrothermal Characteristics by Joule Heating: Application to Terahertz Microbolometer

“…While our microbolometer device arrays have shown reasonable responsivity with improved noise-equivalent power (NEP) for imaging, with potential for application in imaging systems with active THz sources with acceptable integration times, further development is underway. Further, we have also recently reported a chip-integrable solid-state THz source with an AlGaN/GaN-based Schottky barrier lateral HEM-ATT that can deliver a notable ~300 mW, operating at a 1.0 THz frequency [ 48 ]. The microbolometer and source may be suitable for development of compact solid-state spectroscopy systems.…”

AlGaN/GaN bilateral IMPATT device by two-dimensional electron gas for terahertz application

“…Since then, several lateral IMPATT structures have been proposed and shown to have excellent performance. 23,24 However, there is not much literature on the subject at present. There is still great potential for the development of the lateral IMPATT.…”

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

“…One such alternative is the Schottky barrier IMPATT structure [26,27]. In 2023, Khan et al [28] introduced a lateral Schottky barrier IMPATT structure known as the HEM-ATT diode. This innovative device combines elements of a HEMT structure based on AlGaN/GaN two-dimensional electron gas (2-DEG) with a Schottky barrier single-drift region (SDR) avalanche transit-time (ATT) structure [28].…”

“…In 2023, Khan et al [28] introduced a lateral Schottky barrier IMPATT structure known as the HEM-ATT diode. This innovative device combines elements of a HEMT structure based on AlGaN/GaN two-dimensional electron gas (2-DEG) with a Schottky barrier single-drift region (SDR) avalanche transit-time (ATT) structure [28]. The resulting HEM-ATT diode exhibited remarkable capabilities, delivering 300 mW of continuous peak power with an 11% conversion efficiency at 1.0 THz.…”

“…The resulting HEM-ATT diode exhibited remarkable capabilities, delivering 300 mW of continuous peak power with an 11% conversion efficiency at 1.0 THz. This represents a significant leap forward compared to the achievable THz power output and efficiency of conventional double-drift region (DDR) IMPATT sources [28].…”