4 research outputs found
THz parametric gain in semiconductor superlattices in the absence of electric domains
We theoretically show that conditions for THz gain and conditions for
formation of destructive electric domains in semiconductor superlattices are
fairly different in the case of parametric generation and amplification. Action
of an unbiased high-frequency electric field on a superlattice causes a
periodic variation of energy and effective mass of miniband electrons. This
parametric effect can result in a significant gain at some even harmonic of the
pump frequency without formation of electric domains and corruption from pump
harmonics.Comment: 4 pages, 3 figures. Accepted to Appl. Phys. Let
Terahertz Bloch oscillator with suppressed electric domains: Effect of elastic scattering
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.Comment: Submitted to proceedings of the summer school-conference of AQDJJ
programme of ESF, Kiten, Bulgaria, 9-24 June 200