Transport Features in the Topological Phase Hg 0.87 Cd 0.13 Te under Terahertz Photoexcitation
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INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 10–13, 2020
Transport Features in the Topological Phase Hg0.87Cd0.13Te under Terahertz Photoexcitation A. V. Galeevaa,*, A. S. Kazakova, A. I. Artamkina, S. A. Dvoretskyb, N. N. Mikhailovb, M. I. Bannikovc, S. N. Danilovd, L. I. Ryabovae, and D. R. Khokhlova,c a Lomonosov
b
Moscow State University (Faculty of Physics), Moscow, 119991 Russia Rzhanov Institute of Semiconductors Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia c Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991 Russia d Faculty of Physics, University of Regensburg, Regensburg D-93053, Germany e Lomonosov Moscow State University (Faculty of Chemistry), Moscow, 119991 Russia *e-mail: [email protected] Received April 15, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—In this paper, we report on photoconductivity induced by high-power laser radiation with a frequency of 2 THz in Hg0.87Cd0.13Te-based epitaxial structures. Experimental results obtained for a set of the samples with variable geometric parameters allow us to determine the photoresponse features of both bulk and nonlocal contributions to the net response. We show that the persistent photoconductivity effect originates from the non-equilibrium processes related to the bulk carrier excitation. Keywords: photoconductivity, topological phase, cadmium mercury telluride, terahertz spectral range DOI: 10.1134/S1063782620090109
1. INTRODUCTION Hg1 – xCdxTe solid solutions at x < 0.16 are characterized by an energy-band inversion, the absence of a band gap [1, 2], and classified as a topological phase [3, 4]. For x > 0.16, the normal band structure is formed in the system under consideration. Modern methods of epitaxial synthesis make it possible to obtain structures based on Hg1 – xCdxTe with a low concentration of free carriers in the bulk [5, 6]. Under conditions of rather low concentrations of bulk carriers, cadmium mercury telluride exhibits a high photosensitivity in the infrared and terahertz spectral ranges. In combination with the ability of controlling the parameters of the energy spectrum by varying the composition x, it makes possible the consideration of these objects as key materials of infrared and terahertz optoelectronics [7–10]. In Hg1 – xCdxTe-based epitaxial structures with an inverse spectrum, we previously observed positive photoconductivity stimulated by powerful terahertz laser pulses [11, 12]. The appearance of a positive photoresponse can be caused not only by the excitation of carriers in the bulk but also due to nonequilibrium processes in the region of the heterointerfaces of the structure. It can be assumed that the presence of an additional contribution not related to the bulk leads to manifestation of the photoresponse features in the
topological Hg1 – xCdxTe phase in a magnetic field [13]. In this study, we analyze the modification of the kinetics of terahertz photoconductivity by varying the effective bulk co
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