AVS 53rd International Symposium
    Electronic Materials and Processing Wednesday Sessions
       Session EM-WeM

Paper EM-WeM2
Formation and Ordering of Ga Droplets Using a Focused Ion Beam

Wednesday, November 15, 2006, 8:20 am, Room 2003

Session: New Directions in Compound Semiconductors
Presenter: W. Ye, University of Michigan
Authors: W. Ye, University of Michigan
B.L. Cardozo, University of Michigan
X. Weng, Penn State University
J.F. Mansfield, University of Michigan
R.S. Goldman, University of Michigan
Correspondent: Click to Email
The directed self-assembly of low-dimensional semiconductor structures has been achieved using a variety of approaches to producing topographical patterns. However, an approach for achieving highly ordered arrangements of nanostructures with well-controlled shapes and size distributions has yet to be developed. Therefore, we are exploring the formation mechanisms of Ga droplets which may in turn be used for the directed seeding of semiconductor nanopillars. Using a Ga focused ion beam, we have investigated the formation and ordering of Ga droplets on a variety of semiconductor surfaces. On GaAs and GaSb surfaces, randomly distributed Ga droplets are observed above a critical dose (~4E16/cm^2). Subsequent ion beam irradiation results in growth and coalescence of the droplets. On silicon surfaces irradiated with similar doses, droplets are not observed, suggesting a droplet formation mechanism associated with preferential group V element sputtering, and subsequent local Ga agglomeration. Under further irradiation, Ga droplet motion is observed, possibly due to Marangoni motion. Interestingly, a higher droplet velocity is observed on GaSb than on GaAs surfaces, suggesting that droplet motion is dependent on the energetics of the Ga-substrate interface. To obtain ordered Ga droplets, we have milled arrays of holes with uniform sizes and shapes. By controlling the ion beam energy, current, and position, hole arrays with various sizes, depths, and periodicities may be produced. After scanning the ion beam over the patterned area, Ga atoms agglomerate within the holes, leading to the formation of ordered arrays of nearly uniformly-sized Ga droplets. We will also discuss the interaction of Ga droplets with various N-source gases, including the formation of GaN-rich nanocrystals upon exposure to ammonia vapor. @FootnoteText@ This work was supported by an Intelligence Community Postdoctoral Fellowship, the Radcliffe Institute of Advanced Study, NSF-NER, and AFOSR-MURI.