1557 ISSN 1063-7826, Semiconductors, 2017, Vol. 51, No. 12, pp. 1557–1561. © Pleiades Publishing, Ltd., 2017. Original Russian Text © V.V. Rumyantsev, A.M. Kadykov, M.A. Fadeev, A.A. Dubinov, V.V. Utochkin, N.N. Mikhailov, S.A. Dvoretskii, S.V. Morozov, V.I. Gavrilenko, 2017, published in Fizika i Tekhnika Poluprovodnikov, 2017, Vol. 51, No. 12, pp. 1616–1620. Investigation of HgCdTe Waveguide Structures with Quantum Wells for Long-Wavelength Stimulated Emission V. V. Rumyantsev a, b *, A. M. Kadykov a , M. A. Fadeev a , A. A. Dubinov a, b , V. V. Utochkin a, b , N. N. Mikhailov c, d , S. A. Dvoretskii c , S. V. Morozov a, b , and V. I. Gavrilenko a, b a Institute for Physics of Microstructures, Russian Academy of Sciences, Nizhny Novgorod, 603950 Russia b Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, 603950 Russia c Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia d Novosibirsk State University, Novosibirsk, 630090 Russia *e-mail: rumyantsev@ipm.sci-nnov.ru Submitted June 5, 2017; accepted for publication June 15, 2017 Abstract—The photoluminescence and stimulated emission during interband transitions in quantum wells based on HgCdTe placed in an insulator waveguide based on a wide-gap CdHgTe alloy are studied. Hetero- structures with quantum wells based on HgCdTe are of interest for the development of long-wavelength lasers in the range of 25–60 μm, which is currently unattainable for quantum-cascade lasers. Optimal designs of quantum wells for attainment of long-wavelength stimulated emission under optical pumping are discussed. It is shown that narrow quantum wells from pure HgTe appear to be more promising for long-wavelength lasers in comparison with wide (potential) wells from the alloy due to the suppression of Auger recombina- tion. It is demonstrated that molecular-beam epitaxy makes it possible to obtain structures for the localization of radiation with a wavelength of up to 25 μm at a high growth rate. Stimulated emission is obtained for wave- lengths of 14–6 μm with a threshold pump intensity in the range of 100–500 W/cm 2 at 20 K. DOI: 10.1134/S106378261712017X 1. INTRODUCTION At present, the development of compact semicon- ductor lasers for spectroscopy in the far infrared (IR) and terahertz ranges remains a high-priority task. In the mid-IR range, unipolar quantum-cascade lasers (QCLs) exhibit the best performance: in the wave- length range of 5–16 μm, these devices are capable of generation in the continuous mode even at room tem- perature [1]. Terahertz QCLs are also being actively developed [2]. Nevertheless, there is a wide spectral range (wavelengths of 20–60 μm; frequencies of 5– 15 THz), which is still not suitable for QCLs due to high lattice absorption in GaAs and InP materials, which are commonly used for the production of QCLs for this range. The use of QCLs based on InAs [3, 4] made it possible to attain wavelengths of ~20 μm at room temperature, but in a longer wavelength range of 20–25 μm they are used for individual frequencies only, corresponding to phonon-absorption minima in the corresponding materials [5–7]. Thus, the spectral range of 25–60 μm is currently covered by injection lasers only, based on lead chalcogenides PbSnSe(Te), which provide generation at wavelengths of up to 46.5 μm [8, 9] but possess a low output power and operating temperature below the temperature of liquid nitrogen. As alloys based on chalcogenides of lead and tin, the alloy of HgCdTe (mercury–cadmium–tellurium, MCT) can vary the band gap and provide fairly low frequencies of optical phonons for the development of long-wavelength lasers; the energy of CdTe-like opti- cal phonons in narrow-gap MCT compositions is about 20 meV, and of HgTe-like ones is about 15 meV [10]. An advantage of materials based on HgCdTe compared to structures based on PbSnSe(Te) is a more developed growth technology. At present, molecular-beam epitaxy (MBE) makes it possible to obtain high-quality epitaxial films not only on CdZnTe substrates, which are commonly used for the growth of HgCdTe, but also on alternative GaAs sub- strates [11]. The high optical quality of epitaxial struc- tures on GaAs (013) substrates was confirmed by stud- ies of photoconductivity (PC) and photolumines- cence (PL) in the mid- and far-IR ranges [12, 13]. In addition to bulk layers with a low “dark” carrier con- centration (~10 14 cm –3 ), MBE can be used to obtain HgCdTe quantum-well heterostructures with in situ ellipsometric control of the composition and layer thickness [14, 15]. As shown in [14, 15], this recently XXI INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 13–16, 2017