Terahertz Bloch Oscillator With Suppressed Electric Domains: Effect of Elastic Scattering

Abstract

We theoretically consider the amplification of THz radiation in a superlattice Bloch oscillator. The main dilemma in the realization of THz Bloch oscillator is finding operational conditions which allow simultaneously to achieve gain at THz frequencies and to avoid destructive space-charge instabilities. A possible solution to this dilemma is the extended Limited Space-Charge Accumulation scheme of Kroemer (H. Kroemer, cond-mat/0009311). Within the semiclassical miniband transport approach we extend its range of applicability by considering a difference in the relaxation times for electron velocity and electron energy. The kinetics of electrons and fields establishing a stationary signal in the oscillator is also discussed.

High frequency conductivity of hot electrons in carbon nanotubes

“…Then after the differential conductivity turns positive when ω > 1.8T Hz until the maximum peak is attained at ω ≈ 4.5T Hz and then decrease when ω > 4.5T Hz for both zz-CNT and ac-CNT. The Positive Differential Conductivity (PDC) is considered as one of the conditions for electric stability of the system [34] and indicative for terahertz gain without the small spike or fluctuations of electrons associated with NDC that amplifies, induces space charge accumulation and finally develops into electric field domain [35]. The electrical domain development and transporting induce unstable non uniform electric field distribution, which in turn prevents the operation of the Bloch oscillations.…”

“…The electrical domain development and transporting induce unstable non uniform electric field distribution, which in turn prevents the operation of the Bloch oscillations. Thus suppressing domain formation is a prerequisite to observe Bloch oscillations necessary for terahertz gain [35].…”

Theoretical Analysis of Terahertz Frequency Multiplier Based on Semiconductor Superlattices

“…In this case, up to the 6th harmonic from the superlattice frequency multiplier can be realized at room temperature [ 28 ]. Moreover, strong terahertz gain in the superlattice oscillators can be achieved by avoiding space-charge instabilities if driving frequency reaches terahertz range [ 29 , 30 ].…”