White electroluminescent nanostructures in silicon fabricated using focused ion implantation

The use of an accelerator fed microbeam as an implanter enables highest flexibility in doping substrates. Dopant, implantation dose, and pattern can be chosen individually and adopted to sequentially implanted structures. On the other hand, high throughput of arbitrarily shaped and identically doped samples, as needed in semiconductor device fabrication, can be achieved in conjunction with the Bochum Ion Projector. This machine is capable of focusing an ion beam down to 300 run and allows both, prototyping and small series production of devices without the need of a coating mask on the substrate surface. We report on a method for producing nanoscale white light emitting structures by focused ion beam implantation in crystalline silicon. Focused ion beam implantation of acceptor ions into n-type doped Si yields lateral npn-junctions. These junctions emit light from their nanoscale depletion zones if operated in (reverse biased) breakdown mode, depending on voltage polarity on either side of the implanted area. The actual ion beam diameter is not a limiting factor for the submicron width light sources because radiation originates only from depletion zones with lateral sizes in the order of 100 mn. Compatibility with standard silicon processing allows monolithic integration of such light sources in conventional circuit designs. Their emission spectrum covers the whole visible range without showing sharp peaks. However, three distinct maxima can be observed. Their positions and relative heights slightly vary with implantation dose and applied voltage. (C) 2001 Elsevier Science B.V. All rights reserved.