Defect Engineering in Nanoscale Semiconductors through Surface Chemistry

In the same way that gases react with surfaces from above, bulk point defects such as interstitial atoms and vacancies can react from below. Little attention has been paid to this form of surface chemistry, although it is very important for nanoscale semiconductor devices where all regions are in close proximity to a surface or interface. Recent solid-state diffusion measurements and modeling in our laboratory have shown that reactions between defects and semiconductor surfaces can play the dominant role in regulating defect concentrations. Furthermore, the rates of these reactions can be controlled through submonolayer gas adsorption. There are two separate mechanisms for using the surface to control bulk defect concentrations. The first mechanism involves reflecting charged defects from the surface due to electrically active surface defects that set up a repulsive electric field. The second mechanism involves the exchange of defects with surface dangling bonds. Taken together, these observations point to entirely new possibilities for controlling and manipulating defects in semiconductor nanostructure fabrication.