Near band-edge and excitonic behavior of GaAsN epilayers grown by Chemical Beam Epitaxy
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Near band-edge and excitonic behavior of GaAsN epilayers grown by Chemical Beam Epitaxy J.A.H Coaquira,1 L. Bhusal, 1,2 W. Zhu, 1,2 A. Fotkatzikis1,2, M.-A. Pinault, 1 A.P. Litvinchuk, 1,2 and A. Freundlich 1,2,∗ 1
Photovoltaic and Nanostructure Group and Raman laboratory, Texas Center of Superconductivity and Advanced Materials, University of Houston, #724, S&R 1, Houston TX 77204-5004, USA 2 Department of Physics, University of Houston, S&R 1, Houston TX 77204-5004, USA ABSTRACT Photoluminescence and absorption spectroscopy experiments were performed on as grown and thermally annealed GaAs1-xNx with nitrogen content in the range of 0.75-7.1%. At low temperature, the photoluminescence spectra exhibits two set of features: (i) a relatively broad peak at low energy and near to the vicinity of the predicted band gaps and (ii) a sharp excitonic feature at higher energy (about 100 meV for x>4%). Post growth thermal annealing processes systematically favor stronger excitonic emissions, and a notable intensity reduction of the deeper (defect related) luminescence. The low temperature binding energy of the higher energy excitonic peak is found to be consistent with the increase of the electronic effective masses. A careful examination of the data obtained in this work suggests that for higher nitrogen content (x>4%), the fundamental band gap of GaAsN is located at significantly higher energies than those commonly accepted for these alloys. INTRODUCTION Dilute nitrogen containing semiconductor alloys of Ga(In)As have been intensively studied due to their potential for optoelectronic and photovoltaic applications [1-3]. The substitution of arsenic by nitrogen atoms in GaAs produces unusual modifications in the physical properties of these materials. With increasing nitrogen content in the alloy, a large band-gap reduction and a strong increase of the electronic effective mass are observed [3-5]. For relatively low nitrogen content (x
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