Silicon (Si) is one of the most important elements in modern technologies as it forms the backbone of nearly all electronic components from individual transistors to large computer processors. However, one serious drawback of silicon is its unwillingness to emit light. Gallium nitride (GaN) is a wide-bandgap material, which has interesting properties for high-power electronic devices. However, at present this material cannot be fabricated as defect free, and the highest quality is obtained by deposition of GaN on expensive substrates.
The above statements exemplify the desire to teach well-known semiconductor materials new manners. In the semiconductor group, we try to obtain new functionalities and properties by tailoring the material structure on the nanometer scale. We try to teach Si to emit light by embedding it with tin nanocrystals, and by time-resolved fluorescence spectroscopy we examine if these do emit light. For GaN, our aim is to make this material compatible to an inexpensive Si substrate by tailoring novel transition layers between substrate and GaN. Our materials are fabricated by molecular beam epitaxy (MBE), i.e. grown layer-by-layer on the atomic scale. Defects and dislocations are examined by electrical characterization methods and transmission electron microscopy.
Brian Julsgaard is also involved in the SunTune project, which uses nanotechnology to improve the efficiency of solar cells.