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Proposing Institution

Fakultät für angewandte Naturwissenschaften und Mechatronik,
Project Manager

Dr. Hans Christian Alt
Lothstrasse 34
80335 München
Light elements such as H, B, C, N and O are ubiquitous impurities in gallium arsenide bulk crystals and epitaxial layers. Nitrogen has found application in epitaxial techniques to grow ternary dilute nitrides of composition GaAs1-xNx, with x in the range of 0.001 up to some 0.01. These ternary compounds exhibit a strong band gap reduction compared to pure GaAs and are potential candidates for future photovoltaic applications [2]. When studying systematically the infrared (IR) absorption spectra of annealed GaAs crystals doped with carbon, nitrogen and oxygen, Ulrici and Jurisch [3,6] found a sharp and sometimes strong absorption band at 2060 cm-1 occurring after long-term annealing at around 700 °C. Preliminary investigations proposed an CO2 or CO4 defect [8,9], but recently the IR signature was found after N implantation [10], leading to the proposition of a Carbon Nitrogen defect.The main goal of the computational investigation is to find the stable ground-state configuration of CN2 and CN centers in GaAs and the related local mode frequencies. The major work in the project consists in the calculation of total energies of supercell structures with 64 matrix atoms. The calculations will be done with LDA density functional theory using all-electron calculations within the code FHI-aims.[2] M. Henini, Dilute Nitride Semiconductors (Elsevier, Amsterdam, 2005).[3] W. Ulrici and M. Jurisch, Phys. Status Solidi B 242, 2433 (2005).[6] H. Ch. Alt, A. Kersch, and H. E. Wagner, Phys. Status Solidi B 250, 324 (2013).[8] H. Ch. Alt, A. Kersch, and H. E. Wagner, in Int. Conf. on Defects in Semiconductors 2013, AIP Conf. Proc. 1583, 132 (2014).[9] Ch. Kuenneth, unpublished results. [10] H. Ch. Alt, H. E. Wagner, A. Glacki, Ch. Frank-Rotsch, and V. Häublein, Phys. Stat. Solidi B 252, 1827 (2015).

Impressum, Conny Wendler