This Small Business Innovation Research Phase I Project proposes to investigate the fabrication of high-efficiency Si-based visible light emitting diodes (LEDs). These LEDs will be built using Spire's recently discovered method for making efficient contacts to porous silicon by in-situ electropolymerization. In this method, the contact layer is deposited on the entire sponge-like surface of porous silicon in the same hydrofluoric (HF) acid solution used to anodize Si-substrates and form porous layers. By in-situ deposition, the active and fragile Si nanostructures are never exposed to air and, therefore, are not oxidized before contact formation. This clean, simple, and low-cost process for conductive contact formation can effectively eliminate the most serious problem currently preventing the fabrication of an efficient solid-state electroluminescent device based on porous silicon. In Phase I, we will investigate fabrication of two different types of junction LEDs based on in-situ electropolymerized coating of porous silicon. In one device, a heterojunction LED will be formed between an electropolymerized p-type layer and n-type porous silicon film. The second device will consist of a homojunction PN silicon structure with an electropolymerized ohmic contact on top. Phase II will optimize the parameters for fabrication of these LEDs and demonstrate working prototypes worthy of commercialization.
