Band-edge exciton transitions temperature in multiple stacked self-assembled (In 1Kx Mn x )As quantum dot arrays H.C. Jeon a, * , T.W. Kang a , T.W. Kim b , Y.-J. Yu c , W. Jhe c , S.A. Song d a Department of Physics, Quantum-functional Semiconductor Research Center, Dongguk University, 3-26, Pildong, Chungku, Seoul 100-715, South Korea b Division of Electronics and Computer Engineering, Advanced Semiconductor Research Center, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, South Korea c Department of physics, Seoul National University, Seoul 151-747, South Korea d Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, South Korea Received 29 June 2005; accepted 1 July 2005 by A.H. MacDonald Available online 25 July 2005 Abstract Multiple stacked self-assembled (In 1Kx Mn x )As quantum-dot (QD) arrays were grown on GaAs (100) substrates by using molecular-beam epitaxy with a goal of producing (In 1Kx Mn x )As QDs with a semiconductor phase and a high ferromagnetic transition temperature (T c ). Atomic force microscopy, magnetic force microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray fluorescence measurements showed that crystalline multiple stacked (In 0.84 Mn 0.16 )As with symmetric single-domain particle were formed on GaAs substrates. Near-field scanning optical spectroscopy spectra at 10 K for the (In 0.84 Mn 0.16 )As multiple stacked QDs showed that the band-edge exciton transitions were observed. The magnetization curve as a function of the magnetic field at 5 and 300 K indicated that the multiple stacked (In 0.84 Mn 0.16 )As QDs were ferromagnetic, and the magnetization curve as a function of the temperature showed that the T c was as high as 400 K. These results provide important information on the optical and magnetic properties for enhancing the T c of (In 1Kx Mn x )As-based nanostructures. q 2005 Elsevier Ltd. All rights reserved. PACS: 73.63.Kv; 75.60.Ej; 78.67.Hc Keywords: A. Nanostructures; A. Semiconductors; D. Optical properties Diluted magnetic semiconductor (DMS) materials have attracted attention because of the interest in both investi- gations of fundamental physical properties and promising applications for various spintronic devices [1–8]. Among the many DMS structures, (In 1Kx Mn x )As/GaAs ferromag- netic semiconductor quantum structures have become particularly attractive due to their potential applications in spintronic devices because they have the combined properties of both InAs semiconductors and Mn ferromagnetic compounds and because of the excellent advantages derived by utilizing mature InAs-based hetero- structure technology [9–12]. Also, the fact that multiple stacked (In 1Kx Mn x )As DMS quantum dots (QDs) might be promising candidates for next-generation spin-related electronic and optoelectronic devices due to enhanced quantum confinement effect has driven an extensive effort to increase the ferromagnetic transition temperature (T c ) [11,12]. However, until now, the highest T c obtained from IIIV DMS thin films has been 110 K [7,8]; thus, various studies concerned with increasing the T c of DMS materials have driven extensive efforts with the goal of spintronic devices operating at room temperature. Even though only Solid State Communications 136 (2005) 81–84 www.elsevier.com/locate/ssc 0038-1098/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2005.07.010 * Corresponding author. E-mail address: hcjeon@dongguk.edu (H.C. Jeon).