Abstract-Arsenides-and related III-V materials-based multilayered structures for terahertz applications: Various designs and growth technology

 A.E. Yachmenev. S.S .Pushkarev. R.R. Reznik. R.A. Khabibullin. D.S.Ponomarev.




https://www.sciencedirect.com/science/article/abs/pii/S0960897420300127

The fabrication and investigation of single and multilayered structures have become an essential issue in the past decades since these structures directly define valuable properties and efficiency of widely used terahertz (THz) emitters and detectors. Since the development of molecular-beam epitaxy, as well as other crystal growth techniques, a variety of structural designs has appeared and has been proposed. Since that, an enormous progress has been achieved beginning from the pioneering work on photoconductivity in silicon toward different multilayered heterostructures. The last are now commonly utilized as base components in photoconductive THz emitters/detectors, quantum-cascade lasers for pulsed and continuous-wave THz spectroscopic and imaging systems providing critical fundamental and practical applications at the forefront of scientific knowledge (sensors, flexible electronics, security systems, biomedicine, and others). This review summarizes the developments in different approaches and crystal growth techniques, emphasizing the importance of using single and multilayered arsenides-and related III-V materials-based (phosphides, antimonides, bismuthides) structures to accomplish the needs of modern and existing instruments of THz science and technology.

Abstract-Semiconductor quantum well irradiated by a two-mode electromagnetic field as a terahertz emitter

S. Mandal, T. C. H. Liew, and O. V. Kibis

https://journals.aps.org/pra/accepted/1c073N00Y371251b05b25c53e4bdbb014dfe878cd

We study theoretically the nonlinear optical properties of a semiconductor quantum well (QW) irradiated by a two-mode electromagnetic wave consisting of a strong resonant dressing field and a weak off-resonant driving field. In the considered strongly coupled electron-field system, the dressing field opens dynamic Stark gaps in the electron energy spectrum of the QW, whereas the driving field induces electron oscillations in the QW plane. Since the gapped electron spectrum restricts the amplitude of the oscillations, the emission of a frequency comb from the QW appears. Therefore, the doubly-driven QW operates as a nonlinear optical element which can be used, particularly, for optically controlled generation of terahertz radiation.

Abstract-Optimization of the epitaxial design of high current density resonant tunneling diodes for terahertz emitters

Razvan Baba, Richard A. Hogg

Univ. of Glasgow (United Kingdom)

Benjamin J. Stevens

The Univ. of Sheffield (United Kingdom)

Toshikazu Mukai

Rohm Co., Ltd. (Japan)

Proc. SPIE 9755, Quantum Sensing and Nano Electronics and Photonics XIII, 97552W (February 13, 2016); doi:10.1117/12.2212346

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2492410

We discuss the numerical simulation of high current density InGaAs/AlAs/InP resonant tunneling diodes with a view to their optimization for application as THz emitters. We introduce a figure of merit based upon the ratio of maximum extractable THz power and the electrical power developed in the chip. The aim being to develop high efficiency emitters as output power is presently limited by catastrophic failure. A description of the interplay of key parameters follows, with constraints on strained layer epitaxy introduced. We propose an optimized structure utilizing thin barriers paired with a comparatively wide quantum well that satisfies strained layer epitaxy constraints. 
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Abstract-Bias-free lateral terahertz emitters—A simulation study

R. Granzner^1,a), V. M. Polyakov², V. Cimalla², O. Ambacher² and F. Schwierz¹


1 Fachgebiet Festkörperelektronik, Technische Universität Ilmenau, Postfach 100565, 98684 Ilmenau, Germany
2 Fraunhofer Institut für Angewandte Festkörperphysik, Tullastrasse 72, 79108 Freiburg, Germany
a) Author to whom correspondence should be addressed. Electronic mail: ralf.granzner@tu-ilmenau.de
J. Appl. Phys. 118, 043102 (2015); http://dx.doi.org/10.1063/1.4927267

http://scitation.aip.org/content/aip/journal/jap/118/4/10.1063/1.4927267

The design and performance of bias-free InN-based THz emitters that exploit lateral photocurrents is studied by means of numerical simulations. We use a drift-diffusion model with adjusted carrier temperatures and mobilities. The applicability of this approach is demonstrated by a comparison with results from Monte-Carlo simulations. We consider a simple but robust lateral emitter concept using metal stripes with two different thicknesses with one of them being thin enough to be transparent for THz radiation. This arrangement can be easily multiplexed and the efficiency of this concept has already been demonstrated by experiment for GaAs substrates. In the present study, we consider InN, which is known to be an efficient photo-Dember emitter because of its superior transport properties. Our main focus is on the impact of the emitter design on the emission efficiency assuming different operation principles. Both the lateral photo-Dember (LPD) effect and built-in lateral field effects are considered. The appropriate choice of the metal stripe and window geometry as well as the impact of surface Fermi level pinning are investigated in detail, and design guidelines for efficient large area emitters using multiplexed structures are provided. We find that InN LPD emitters do not suffer from Fermi level pinning at the InN surface. The optimum emission efficiency is found for LPD emitter structures having 200 nm wide illumination windows and mask stripes. Emitter structures in which lateral electric fields are induced by the metal mask contacts can have a considerably higher efficiency than pure LPD emitters. In the best case, the THz emission of such structures is increased by one order of magnitude. Their optimum window size is 1 μm without the necessity of a partially transparent set of mask stripes.