Tunable terahertz-frequency resonances and negative dynamic conductivity of two-dimensional electrons in group-III nitrides

Abstract

We investigated the terahertz (THz)-frequency resonances of two-dimensional electron conductivity under the streaming transport in a GaN quantum well at the nitrogen temperature. The calculation results found that the negative microwave mobility can occur in the narrow windows near the optical-phonon transit-time resonance frequencies, which can be tuned electrically in the 0.2–2.5THz range with the static electric fields of 1–10kV∕cm. The estimated magnitude of the negative mobility reaches hundreds of cm2∕Vs. These effects suggest that the nitride-based heterostructure may enable the development of an electrically pumped, tunable THz source operating at or above 77K.

Generation of TeraHertz radiation assisted by optical phonons in nitride‐based quantum wells and heterolayers

“…Recent MC simulations [1,4,5] confirm significant increase of the maximum generation frequency under 2D transport with respect to bulk materials. Since 2D transport is usually realized experimentally in quantum-wells (QW) and single-interface hetero-layers (HL), the aim of this work is to consider theoretically the possible applications of these structures for the generation of THz radiation and to compare their characteristics with bulk materials.…”

<title>Generation of coherent terahertz radiation due to optical-phonon emission assisted transit-time resonance in quantum wells and heterolayers</title>

“…For this sake, the characteristic scattering times, τ − and τ + inside and outside of the optical-phonon sphere, respectively (the so called passive and active regions), must satisfy the inequality: τ − >> τ E >> τ + , where τ E = p 0 /eE is the electron transit-time inside the optical-phonon sphere with radius p 0 under a constant applied electric field E. The recent trend is to make use of two-dimensional (2D) electron transport. 3,4 The main advantages are: (i) an increase of the maximum generation frequency f gen = 1/τ E due to a more abrupt threshold of the optical-phonon emission scattering rate 3, 4 (improvement of right inequality), (ii) the possibility to use high carrier densities avoiding impurity scattering (improvement of left inequality). Since a 2D-transport is usually realized experimentally in two main cases corresponding to quantum-wells (QW) and heterolayers (HL), the aim of this work is to consider theoretically the possible applications of these structures for the generation of THz radiation.…”

Influence of interface roughness on two-dimensional electron gas streaming transport in GaN-based heterostructures

“…[7][8][9] Recently, the streaming transport of the two-dimensional electron gas in III-nitride heterostructures has been addressed, [10][11][12] where possible advantages of the two-dimensional ͑2D͒ streaming transport compared to the three-dimensional ͑3D͒ case are discussed. However, in these works the influence of the interface roughness on 2D electron gas ͑2DEG͒ transport was neglected.…”