Cu Induced Optical Transitions in MOCVD Grown Cu Doped GaN
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0892-FF23-08.1
Cu Induced Optical Transitions in MOCVD Grown Cu Doped GaN Jayantha Senawiratne1, Martin Strassburg1,2, Adam Payne2, Ali Asghar2, William Fenwick2, Nola Li2, Ian Ferguson2, and Nikolaus Dietz1,∗ 1 Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30303-4106, U.S.A. 2 Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30322-0250, U.S.A. ABSTRACTS Optical and structural properties of in situ Cu doped GaN thin films grown on sapphire substrates were optically investigated by means of Raman, photoluminescence (PL), and absorption spectroscopy. Different Cu concentrations in the films were analyzed by secondary ion mass spectroscopy (SIMS) and found to vary from 2x1016 cm-3 to 5x1017 cm-3. Raman studies confirmed high crystalline quality of GaN:Cu with no major structural damages due to Cu incorporation. PL investigation revealed that the origin of the emission around 2.4 eV is most likely due to Cu incorporation. The electrical conductivity of the samples was analyzed by Hall measurements and the found semi-insulating behavior was assigned to the compensation of intrinsic donors by the deep Cu acceptor states.
INTRODUCTION Copper incorporated in GaN on lattice sites acts as double acceptor and has therefore attracted increasing attention in the recent years. High–Ohmic material can be fabricated because of the deep acceptor-like states introduced by Cu that compensate residual donors [1]. Using Coulomb pairing, Cu was applied for co-doping purposes that have been applied to create shallow acceptor complexes [2]. Furthermore, copper electronic properties as a transition metal renders it as a candidate for spintronics material. The Cu dopants can be introduced into GaN during the growth or by ion implantation. Ion implantation has become more popular, because it is a more controlled and a precise method of doping a selective area of the sample. However, crystalline damage during the ion implantation is unavoidable, since it is a thermodynamically unstable method [3,4]. Therefore, application of in situ doping of Cu has an advantage since this process does not introduce damage to the lattice structure. This work reports on the in situ incorporation of Cu in metal organic chemical vapor deposition (MOCVD) grown GaN. In addition to that, structural and Cu induced optical transitions were investigated by different means of optical spectroscopy. EXPERIMENTAL DETAILS Cu doped GaN layers on sapphire substrates were grown by metal organic chemical vapor deposition (MOCVD), using ammonia and trimethyle gallium (TMGa) as nitrogen and gallium sources, respectively. In addition, different Cu concentrations in the layers were introduced ∗
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during the growth by varying the flow of the Cu source, (N,N'-Diisopropylacetamidinato) copper(I), to the reactor. The precursors were transferred to the reactor using hydrogen gas flow. The stoichiotric analysis of the Cu concentration in the films were performed
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