Auger quenching-based modulation of electroluminescence from ion-implanted silicon nanocrystals

Abstract

We describe high-speed control of light from silicon nanocrystals under electrical excitation. The nanocrystals are fabricated by the ion implantation of Si+ in the 15?nm thick gate oxide of a field effect transistor at 6.5?keV. A characteristic read-peaked electroluminescence is obtained either by DC or AC gate excitation. However, AC gate excitation is found to have a frequency response that is limited by the radiative lifetimes of silicon nanocrystals, which makes impossible the direct modulation of light beyond 100?kb?s?1 rates. As a solution, we demonstrate that combined DC gate excitation along with an AC channel hot electron injection of electrons into the nanocrystals may be used to obtain a 100% deep modulation at rates of 200?Mb?s?1 and low modulating voltages. This approach may find applications in biological sensing integrated into CMOS, single-photon emitters or direct encoding of information into light from Si-nc doped with erbium systems, which exhibit net optical gain. In this respect, the main advantage compared to conventional electro-optical modulators based on plasma dispersion effects is the low power consumption (104 times smaller) and thus the inherent large scale of integration. A detailed electrical characterization is also given. An Si/SiO2 barrier change from ?b = 3.2 to 4.2?eV is found while the injection mechanism is changed from Fowler?Nordheim to channel hot electron, which is a clear signature of nanocrystal charging and subsequent electroluminescence quenching.