Inhomogeneous linewidth broadening and radiative lifetime dispersion of size dependent direct bandgap radiation in Si quantum dot

Abstract

The SiOx (SiOx:Si-QDs) with buried Si quantum dots (Si-QDs) is synthesized by plasma-enhanced chemical vapor deposition (PECVD), and the size-dependent wave-function of Si-QDs embedded in Si-rich SiO2 matrix is experimentally and theoretically analyzed to reformulate its bandgap energy as Eg(d) = 1.12+5.83/d1.78. The photoluminescent lifetime of Si-QDs is dominated by the non-phonon assisted radiative recombination. Shrinking the Si-QD size from 4.3 to 1.9 nm increases the overlapping probability of electron-hole wave-functions in Si-QD to shorten the non-phonon assisted radiative lifetime from 6.3 μs to 83 ns. Fitting the time-resolved photoluminescence trace with a stretched exponential decay function reveals a lifetime dispersion factor. The lifetime dispersion greatly reduced from 0.8 to 0.39 by enlarging the size distribution of Si-QDs from 0.2 to 1.1 nm, which elucidates the inhomogeneous linewidth broadening feature of Si-QDs. Based on the simulation of non-phonon assisted recombination process, the full-band stretched exponential decay analysis confirms the correlation between inhomogeneous linewidth broadening and lifetime dispersion in Si-QDs.