Three‐Terminal Graphene Nanoribbon Tunable Avalanche Transit Time Sources for Terahertz Power Generation

Abstract

Herein, the possibilities of tuning oscillation frequency and power in terahertz (THz) graphene nanoribbon (GNR)‐based avalanche transit time (ATT) sources by introducing a third terminal on their planar structure are discussed. In this regard, a three‐terminal planner impact ATT (IMPATT) structure based on GNR on oxide (SiO2) is proposed. Inherent power combining capabilities of parallel‐connected IMPATT structures are utilized to increase the power output at THz frequencies. Static, high frequency, and noise simulations are carried out using in‐house simulation codes based on self‐consistent quantum drift–diffusion model. Results show that around 0.7–5.3% and 9.0–13.3% modulation of frequency and power output are achievable, respectively, in the GNR IMPATT oscillators operating in the frequency range of 1.0–10.0 THz, respectively, by applying a suitable amount of voltage at the third or controlling terminal; however, the enhancement of noise level at the output is observed to be insignificant as a result of using the active third‐terminal control.

Terahertz wave radiation from mutually injection locked multi‐element graphene nanoribbon avalanche transit time sources

“…Schematics of cross‐sectional as well as top view of a mutually injection locked five‐element G‐IMPATT source are illustrated in Figure 1A,B, respectively. The n + ‐ n ‐ p ‐ p + structured double‐drift region (DDR) IMPATT diodes based on monolayer (ML) GNR strips can be fabricated on SiO 2 ; the fabrication steps of parallel G‐IMPATT diodes on SiO 2 (insulator) substrate as well as process of making contacts to form electrode (common anode and cathode) for DC biasing have already been described by the author in earlier reports 33,34 . The coupling circuits between adjacent G‐IMPATT diodes can be implemented via planar microstrip lines.…”

“…Most exciting feature of the said parallel‐connected‐power‐combined (PCPC) mode G‐IMPATT oscillator is its high power delivering capability, which is in the order of milli‐watts (mW) even above 5.0 THz 33 . Another, astonishing fact is that a third controlling terminal can also be incorporated in the said source for realizing voltage‐controlled THz radiator 34 . However, the author did not utilize the mutual injection locking between the elements of these sources for their PCPC mode of operation.…”

“…[30][31][32] Another very interesting power combined solid-state oscillator has recently been proposed by the author, which is based on parallel connected graphene nanoribbon (GNR) based impact avalanche transit time (G-IMPATT) diodes. 33,34 Most exciting feature of the said parallel-connected-power-combined (PCPC) mode G-IMPATT oscillator is its high power delivering capability, which is in the order of milli-watts (mW) even above 5.0 THz. 33 Another, astonishing fact is that a third controlling terminal can also be incorporated in the said source for realizing voltage-controlled THz radiator.…”

“…33 Another, astonishing fact is that a third controlling terminal can also be incorporated in the said source for realizing voltage-controlled THz radiator. 34 However, the author did not utilize the mutual injection locking between the elements of these sources for their PCPC mode of operation. As a result of that, the simulations carried out by the author may overestimate the THz power output for those sources.…”

“…In practical case, PCPC mode G-IMPATT source without the provision of mutual injection locking can radiate a number of frequencies with smaller power due to the obvious mismatch between the elements (G-IMPATT diodes) of the oscillator; therefore, effective power combination is almost impossible to achieve, since the fabrication of exactly identical diodes having dimensions in the order of nanometers (nm) is not possible by using the state-of-the-art technology. 33,34 That is why, in the present paper a method of mutual injection locking between the elements of the source via planar circuit based coupling between adjacent elements has been proposed and analyzed. At first the analysis for the two-element coupled oscillator has been presented.…”