Impact of blue-shifted effective joint density of electronic states on the photoluminescence of nanostructured silicon

• Published in: Journal of luminescence Vol. 273; p. 120658
• Main Authors: Basu, Shayari, Ghanta, Ujjwal, Roy Chowdhury, Subhajit, Pramanik, Manotosh, Roy, Samrat, Das, Ashok, Bandyopadhyay, Sudipta, pal, Bipul, Hossain, Syed Minhaz
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2024
• Subjects: Density of states; Intrinsic transition; Photoluminescence; Silicon nanostructure; Temperature dependent PL; Transition mechanism; Silicon nanostructure; Transition mechanism; Density of states; Intrinsic transition; Temperature dependent PL; Photoluminescence
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2024.120658

Light emission from nanostructured silicon has triggered tremendous research interest for three decades. Yet, the exact mechanism of photoluminescence from silicon-based nano-systems is still not completely understood. It is generally believed that quantum confinement and surface chemistry play a combined role in determining the luminescence characteristics of nano silicon. In this work, we show that the evolution of electron-hole effective joint density of states, resulting from the relaxation of k-selection rule, can account for the much-observed temperature dependent shift of the luminescence spectra of nanostructured silicon. Deconvolution of the emission characteristics reveals three distinct radiative recombination channels those can be attributed to band-to-band, band-to-trap and trap-to-trap transitions. At temperatures below ∼200 K, the peak due to band-to-band transition exhibit a nearly linear blue shift with increasing temperature while at higher temperatures, this trend is reversed. The rate of variation of emission peak energy with temperature is also found to be dependent on the effective crystallite size. These results are explained in terms of shift in the effective joint density of state function of photogenerated electron-hole pairs. The shift provides experimental evidence of the pseudo-direct transitions in the quantum-confined nanostructure of silicon. [Display omitted] •Broad PL spectrum from nanostructured Silicon obtained as a convolution of multiple radiative decay channels at different temperatures.•Effective joint density of states of photoexcited e-h pair gets broadened and blue shifted for nanostructured silicon.•This study provides a means of estimating the temperature coefficient for the shift in peak energy related to band-to-band transitions.•The work demonstrates the relaxation of the k-selection rule in quantum-confined silicon structure.