Ga 1-x Gd x N-Based Spin Polarized Light Emitting Diode
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Ga1-xGdxN-Based Spin Polarized Light Emitting Diode Muhammad Jamil1, Tahir Zaidi2, Andrew Melton2, Tianming Xu2, and Ian T. Ferguson3 1
Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan
2
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
3
Department of Electrical and Computer Engineering, University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
Keywords: Spin Polarized LED, MOCVD, Nitride DMS *
Corresponding author: e-mail: [email protected], Phone: (704) 687-5885
ABSTRACT In this work, a room temperature spin-polarized LED based on ferromagnetic Ga1-xGdxN is reported. The device was grown by metalorganic chemical vapor deposition (MOCVD) and is the first report of a spin-LED based on Ga1-xGdxN. Electroluminescence from this device had a degree of polarization of 14.6% at 5000 Gauss and retained a degree of polarization of 9.3% after removal of the applied magnetic field. Ga1-xGdxN thin films were grown on 2 µm GaN templates and were co-doped with Si and Mg to achieve n-type and p-type materials. Co-doping of the Ga1-xGdxN films with Si produced conductive n-type material, while co-doping with Mg produced compensated p-type material. Both Si and Mg co-doped films exhibited room temperature ferromagnetism, measured by vibrating sample magnetometry. INTRODUCTION Significant efforts have been made in the field of semiconductor spintronics (SPIN Transport electrONICS) since the discovery of the Giant Magnetoresistance in the late 1980s by Gruenberg and Fert [1]. This class of devices exploits both the electron spin and its charge in order to introduce an additional degree of freedom to the next generation of electronic systems. For device applications to be practical, it is very important that the Curie temperature (TC) of candidate materials is above room temperature (RT). Attention was focused on making III-V semiconductors ferromagnetic by doping them with magnetic ions in the late 1990s [2]. Most of these materials can be described as dilute magnetic semiconductors (DMS), that is, semiconductors which are alloyed with low concentrations of magnetic elements. The most widely studied III-V DMS compound is Ga1-xMnxAs, which is a p-type material based on the shallow nature of the Mn acceptor. This material has been shown to be effective as a spin injection layer in optically based devices [3]. However, the TC of these materials is limited to less than 170 K which precludes their practical use [4]. Still, this material system has resulted in the best spin-LED results, with up to 22.1% electroluminescence polarization at 1 Tesla applied field and 10 Kelvin [5]. In 2000, Dietl et al., employing Zener mean field theory, predicted room temperature ferromagnetism for Ga1-xMnxN and Zn1-xMnxO with 5 % Mn incorporation and 3.5×1020 holes/cm3 [6]. However, to date, transition metal (TM) doping of GaN has resulted in semiinsulating films, and the required hole concentration has not been achieved in either material. As a general phenomenon, TM-
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