abstract
Native defects and unintentional contaminations during growth can strongly influence the optical properties of semiconductors and their applications. The tailoring of these optical properties requires a deep understanding of the role of defects and hence contributes to the improvement of the crystal quality of the epitaxially grown active layer in optoelectronic devices. In this work, a ZnSe single crystal grown by chemical vapour transport was deeply investigated by photoluminescence. The observed luminescence comprises four narrow radiative transitions in the near-band edge, due to free-to-bound recombination processes involving acceptor defects, and three deep defect-related transitions at lower energies, involving the localization of a charge carrier in the electrostatic field created by an electrical charge of the opposite sign with a higher binding energy. In the latter case, the thermal activation of non-radiative de-excitation channels results in the release of the less bound carrier, whose ionization energies are estimated to be in the range of 176-206 meV. For the radiative transition observed at 2.135 eV, the proposed model comprises a donor state and a deeper acceptor state likely related to a Zn vacancy. Although the crystal evidences a low doping level, the density of ionized defects is high enough to determine the dominant dispersion mechanism in the lattice.
keywords
CHEMICAL-VAPOR TRANSPORT; OPTICAL-PROPERTIES; SOLAR-CELL; PHOTOLUMINESCENCE; LUMINESCENCE; DEPENDENCE; DEFECTS; CENTERS; SPECTRA; BAND
subject category
Materials Science; Physics
authors
Kannappan, P; Falcao, BP; Asokan, K; Leitao, JP; Dhanasekaran, R
our authors
Bruno Teixeira de Poças Falcão
Junior Researcheracknowledgements
This work was developed within the scope of the project i3N, UIDB/50025/2020 & UIDP/50025/2020, financed by national funds through the FCT/MEC. P.K. acknowledges the fellowship from the Svagata project through the Erasmus Program. J. P. L. acknowledges the financial support from the project SusPhotoSolutions-SolucoesFotovoltaicasSustentaveis. The authors acknowledge Prof. T. Monteiro, Dr. J. Rodrigues, Dr. N. Ben Sedrine, and Dr. J. P. Teixeira for their help with the PL measurements and the scientific discussions.