Enhancing the electroluminescence efficiency of Si NC/SiO₂superlattice-based light-emitting diodes through hydrogen ion beam treatment

Abstract

This paper presents a novel method for enhancing the electroluminescence (EL) efficiency of ten-period silicon-rich oxide (SRO)/SiO2 superlattice-based light-emitting diodes (LEDs). A hydrogen ion beam (HIB) was used to irradiate each SRO layer of the superlattices to increase the interfacial roughness on the nanoscale and the density of the Si nanocrystals (Si NCs). Fowler-Nordheim (F-N) tunneling was the major mechanism for injecting the carriers into the Si NCs. The barrier height of the F-N tunneling was lowered by forming a nano-roughened interface and the nonradiative Pb centers were passivated through the HIB treatment. Additionally, the reflectance of the LEDs was lowered because of the nano-roughened interface. These factors considerably increased the slope efficiency of EL and the maximum output power of the LEDs. The lighting efficiency increased by an order of magnitude, and the turn-on voltage decreased considerably. This study established an efficient approach for obtaining bright Si NC/SiO2 superlattice-based LEDs.

Size-tunable electroluminescence characteristics of quantum confined Si nanocrystals embedded in Si-rich oxide matrix

“…1,6,31 The linear fitted F-N plot in the high electric field region reveals that the carrier conduction in the fabricated device is dominated by the F-N tunneling mechanism between the NCs through the triangular-shaped SiO 2 barriers. 1,6,31 In a low electric field region below 4.38 Â 10 6 V/cm, the F-N plot becomes non-linear, denoting that the carrier conduction between NCs follows the direct tunneling mechanism through SiO 2 barriers. This kind of carrier transport mechanism combining both F-N tunneling and direct tunneling in different electric field regions has been reported in the literature for similar systems.…”

“…[1][2][3][4] Reducing the dimensions of Si structures below the excitonic Bohr radius of Si ($4.8 nm) results in light emission due to the quantum confinement effect (QCE). [5][6][7][8] Different approaches of light emission through the QCE have been reported to date based on Si nanowires, [9][10][11][12] nanocones, 13,14 colloidal nanocrystals, 15,16 and nanocrystals in the oxide matrix. 5,[17][18][19] Among them, Si nanocrystals (Si NCs) embedded into the SiO 2 matrix are most promising due to chemical stability and wavelength selective size-tunable photoluminescence (PL).…”

“…The demonstrations of electroluminescence (EL) are mostly broad, covering the visible spectral range or defectrelated blue emissions only. 1,[23][24][25][26] L opez-Vidrier et al 27 and Fu et al 6 have recently demonstrated efficient EL in the Si NC/SiO 2 superlattice structure, but they too observed EL over a broad spectral range. Therefore, the demonstration of tunable EL emission utilizing the QCE in Si NCs may provide a colossal step toward optoelectronics in Si platforms.…”

“…So the origin of PL emissions is attributed to the quantum confinement effect in Si NCs in agreement with the results reported by several groups. 1,6,11,18,26 On the other hand, the observation of a faster decay channel (s 1 ) may be due to the presence of interfacial defects between Si NCs and the SiO 2 matrix surrounding it. For further studies of defect-induced carrier dynamics in detail, transient reflectivity (DR) measurements at an ultrafast timescale were carried out for a typical sample (P1000).…”

“…This kind of carrier transport mechanism combining both F-N tunneling and direct tunneling in different electric field regions has been reported in the literature for similar systems. 6,18,31,32 Each of the MOSLEDs fabricated using P900, P1000, and P1060 samples exhibited EL emission of different colors at room temperature, which is visible even in the naked eye. Figures 4(a) and 4(b) present the deconvoluted EL spectra from P900 and P1000 devices, respectively.…”