811 ISSN 1063-7850, Technical Physics Letters, 2017, Vol. 43, No. 9, pp. 811–813. © Pleiades Publishing, Ltd., 2017. Original Russian Text © V.G. Talalaev, I.V. Shtrom, Yu.B. Samsonenko, A.I. Khrebtov, A.D. Bouravleuv, G.E. Cirlin, 2017, published in Pis’ma v Zhurnal Tekhnicheskoi Fiziki, 2017, Vol. 43, No. 17, pp. 71–77. Directional Emission from Beryllium Doped GaAs/AlGaAs Nanowires V. G. Talalaev a, b , I. V. Shtrom b, c, d, e , Yu. B. Samsonenko c, e , A. I. Khrebtov c , A. D. Bouravleuv b, c, d, e , and G. E. Cirlin c, e, f, g * a Martin Luther University, Halle–Wittenberg, Halle, Germany b St. Petersburg State University, St. Petersburg, Russia c St. Petersburg Academic University, Russian Academy of Sciences, St. Petersburg, Russia d Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, Russia e Institute of Analytical Instrumentation, Russian Academy of Sciences, St. Petersburg, Russia f St. Petersburg National Research University of Information Technologies, Mechanics, and Optics (ITMO University), St. Petersburg, Russia g Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia * e-mail: cirlin@beam.ioffe.ru Received September 28, 2016 Abstract—The emission directionality of self-catalytic GaAs nanowires in an AlGaAs shell, produced by molecular-beam epitaxy with a varied level of beryllium doping, is studied. It is shown that an undoped sam- ple possesses pronounced waveguide properties along the growth direction. With increasing doping level, the intensity of the emission directed perpendicular to the lateral nanowire walls grows. DOI: 10.1134/S1063785017090085 At present the properties of nanometer-cross-sec- tion nanowires (NWs), including those intentionally doped, are being intensively studied. This is due to the possibility of using NWs to fabricate various device components, including solar cells, transistors, lasers, and light-emitting diodes [1]. For optoelectronic applications, structures of the type of GaAs NWs in an AlGaAs shell have a significant potential because of the presence of a wide-bandgap capping layer that effectively suppresses the nonradiative recombination processes associated with the high density of the sur- face states in GaAs NWs [2–4]. In addition, this NW configuration opens up new opportunities for engi- neering the electronic structure in radial heterostruc- tures [5, 6]. A study of the intensity of the directional emission both from arrays of vertically standing NWs and from single NWs is of fundamental importance for improving the efficiency of optoelectronic devices. In [7–9], NW-based device structures with p–n junc- tions were demonstrated. In their fabrication, NWs are doped with both p- and n-type impurities (e.g., Be or Si, respectively). It was shown that the optical proper- ties of NWs depend on the dopant concentration [10]. However, the problem of how impurities affect the emission directionality in NWs has been barely stud- ied. Our study is concerned with the near-IR emission directionality diagram in self-catalytic GaAs/AlGaAs NWs doped with various Be concentrations. Growth experiments were carried out on an EP 1203 machine equipped with various effusion sources, including those of aluminum, gallium, arsenic, and beryllium. The surface was examined during the growth by the reflection high-energy electron diffrac- tion (RHEED) method. Polished semi-insulating Si (111) wafers served as substrates. The growth was per- formed by the self-catalytic method developed by the authors [11]. After the oxide layer was removed from the substrate surface, a gallium layer with a thickness of ~2 nm was deposited in the absence of an arsenic flow toward the surface. After holding it for 1 min in order to create more even eutectic Ga drops, As and Be (a p-type dopant in the case of doped NWs) shut- ters were opened and a GaAs NW was grown. The RHEED patterns indicated that a cubic phase is formed in the NW after 50 nm is deposited. Further, the Al shutter was opened to form an AlGaAs capping layer (with a closed beryllium shutter). The hole con- centrations in the NW core found from the growth of GaAs:Be planar layers were 5 × 10 16 and 5 × 10 19 cm –3 (low- and highly doped modes, respectively). To prepare samples for measurements, NW arrays on a substrate were placed in an ethanol solution. Fur- ther, the NWs were ultrasonically separated from the substrate and transferred in a drop onto the surface of a 2 × 2 mm silicon plate (Fig. 1a). The data furnished by an optical microscope enabled us to estimate the