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

Enhancing Optical Nonlinearity in a Nonstoichiometric SiN Waveguide for Cross-Wavelength All-Optical Data Processing

“…8,9 Recently, the free-carrier absorption (FCA) cross-section in the silicon quantum dots (Si-QDs) has been proved to be 1 order of magnitude larger than that in the bulk Si. 10−12 Even though shrinking the Si-QD size can further shorten the carrier relaxation lifetime due to the quantum confinement effect, 13,14 the effective free-carrier lifetime in Si-QDs is still much longer than that of the bulk Si so as to limit the modulation bandwidth of the Si-QD-based FCA modulator at around 1 MHz. 15−17 To develop an ultrafast all-optical modulator that is fully compatible with Si-based CMOS integrated circuits, the most appropriate solution among versatile approaches is to use the enhanced optical nonlinearity of the Si-QDs.…”

All-Optical Cross-Absorption-Modulation Based Gb/s Switching With Silicon Quantum Dots

“…8. Owing to the inhomogeneous size distribution of the Si-QDs [14], the free carrier lifetime dispersion by the Si-QDs will be induced to degrade the modulation response of the SiC x :Si-QD based all-optical XAM switch. In principle, the transient free-carrier absorption induced probe power depletion with excited free carriers excited in the SiC x :Si-QD based 1077-260X (c) 2015 IEEE.…”

“…The QCE induced by Si-QD broadens the wave function of e-h pairs to facilitate for the formation of the quasi-direct bandgap and to stimulate the carrier recombination without assistance of phonon [14,15]. Therefore, the Si-QD based optoelectronics have been developed in recent years [16][17][18][19][20][21].…”

“…In principle, the FCA cross-section of the Si-QD can be affected by the QCE, such that the free carrier lifetime as well as the FCA modulation bandwidth can be manipulated by controlling the size of the Si-QD. The latter works have declared that the bandgap property as well as carrier lifetime of Si-QD can be significantly modified by shrinking the Si-QD size [14,27]. For example, the carrier lifetime can be significantly shortened to ~ns by introducing QCE effect and defect state in the SiO 2 or SiN x matrix [28][29][30], which benefits from the improvement on the modulation bandwidth to 10s-100s MHz.…”

All-Optical Modulation in Si Quantum Dot-Doped SiO Micro-Ring Waveguide Resonator

“…[10][11][12][13][14][15][16][17][18]. Since the first observation of optical gain from Si-QDs by Pavesi et al in 2000 [19], the relationship between the Si-QDs size and luminescent quantum efficiency was investigated [20][21][22][23][24][25]. However, the optical gain of Si-QDs is still lower than that of III-V compound semiconductor materials, which results from the gain saturation effect of the Si-QDs [26][27][28].…”