The development of efficient light emitting devices in silicon would lead to major advances in the microelectronics industry and suggest a radically different approach to the development of optical communications as well as other key applications in the future.
There has been much recent progress in the field of silicon-based light emitting devices with several key reports of silicon-based devices that operate at room temperature with practical efficiencies. We show here developments of one of the most promising technologies - Dislocation Engineering. A key benefit of this technology, difficult to over emphasize, given the huge "tool-up" costs in the microelectronics industry, is that all the process steps are completely compatible with ULSI technology. Conventional implantation technology, using the standard dopant species are used to make light emitting diodes (LEDs) in crystalline silicon that operate efficiently at room temperature under forward bias.
Dislocation loop arrays, formed by ion implantation, are used to produce a strain field that can be made to modify the band gap of the silicon in such a way that the silicon itself can be used to provide spatial confinement of carriers. This enables the non-radiative recombination in the bulk and at the surface to be decoupled allowing efficient radiative recombination to occur in the active region of the device. Boron implantation has been used to form both the dislocation loop array and the p-type dopant to form a p-n junction in n-type silicon. The device operates conventionally under forward bias. Unpackaged LEDs are achieving external power efficiencies, at room temperature, of up to 0.1%, comparable, to that achievable in conventional III-V infra-red LEDs. Here we will also discuss methods of tuning the emission wavelength of the device over the important 1.1 to 1.7 μ m range.
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