However, even if GaAs high-quality devices already exist, they still remain a great technological challenge to combine both Si- and GaAs-based blocks in the same processor chip since it is difficult to grow high-quality GaAs layers on an Si substrate. 8 This is why the technology of electro-optic devices is based mainly on direct gap III–V semiconductors, such as GaAs. Unfortunately, Si has an indirect bandgap that prevents electron recombination light emission. 1 – 3 Therefore, great efforts are conducted to obtain light-emitting Si-based devices as building blocks of integrated optical and electrical processing.
It is commonly accepted that one of the best ways to overcome these interference problems is to use optical communication instead of electrical ones since photons do not interact between them. The need for higher processing speed imposes a great technological challenge since reducing the internal distance between the processor transistors increases RF interference phenomena due to the electron-motion-induced electric field in the internal communication path. Moreover, the location of the radiative recombination source inside the channel, responsible for the light emission, is also controllable through the applied voltages. The emitted light intensity can be electrically controlled by the drain voltage V ds while the peak emission wavelength depends on the channel thickness and slightly on V ds. The results show that this device can emit near infrared radiation in the 1 to 2 μ m range, compatible with the optical networking spectrum.
The device’s coupled optical and electrical properties have been simulated for channel thicknesses, varying from 2 to 9 nm. This quantum well consists of a recessed ultrathin silicon layer, obtained by a gate-recessed channel and limited between two oxide layers. Overcoming the silicon indirect bandgap with special geometry, we developed a concept of a metal–oxide–semiconductor field-effect transistor, based on a silicon quantum well structure that enables control of light emission. In the race to realize ultrahigh-speed processors, silicon photonics research is part of the efforts.
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