The radiative and nonradiative recombinations involved in efficient light-emitting metal-oxide-silicon tunneling diodes have been studied. The radiative recombination coefficient in the silicon light-emitting diode was previously found by us to be one order of magnitude greater than that of the bulk silicon. However, the nonradiative Shockley-Read-Hall recombination still dominates the carrier recombination processes near the Si/SiO<sub>2</sub> interface. In the present work, we show by using the voltage-dependent photoluminescence that the position of the Fermi level near the Si/SiO<sub>2</sub> interface significantly influences the nonradiative recombination rates. The nonradiative recombination states are shown to capture electrons much more effectively. This study suggests that significant reduction in nonradiative recombination is essential for efficient light emission from silicon.
We report the finding of photoluminescence (PL) and electroluminescence (EL) studies at silicon bandgap energy for the indium-tin-oxide (ITO)/SiO<sub>2</sub>/Si metal-oxide-semiconductor (MOS) tunneling diodes. The characteristics of temporal EL response, temperature dependence of EL and PL intensities, and voltage-dependent PL intensity, were used to investigate the radiative recombination and nonradiative Shockley-Read-Hall (SRH) recombination near the Si-SiO<sub>2</sub> interface. The temporal EL response indicates that the radiative recombination coefficient in the light-emitting MOS tunneling diode is about ten times larger than that of the bulk silicon. However, the nonradiative SRH recombination is still the dominant carrier recombination process. The intensity of EL was found to be lesser sensitive with temperature than that of PL, which indicates that the nonradiadiative recombination is less thermally active and less efficient for EL. The voltage-dependent PL study shows that the PL intensity increases with the bias voltage. This observation is attributed to the variations of nonradiative SRH recombination rates due to the change of Fermi level with the bias voltage. This study shows that the nonradiative recombination near the Si-SiO<sub>2</sub> interface strongly influences the luminescent efficiency.