AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS+EM+SC-ThA

Paper SS+EM+SC-ThA7
Ion Induced Step Debunching of GaN

Thursday, November 18, 2004, 4:00 pm, Room 210C

Session: Compound Semiconductor Growth and Surface Structure
Presenter: B. Cui, University of Minnesota
Authors: B. Cui, University of Minnesota
P.I. Cohen, University of Minnesota
A.M. Dabira, SVT Associates, Inc.
Correspondent: Click to Email
The development of surface morphology during ion bombardment has been described in terms of the curvature dependence of the sputtering yield [1] and asymmetric kinetics for the attachment of surface adatoms and vacancies at step edges [2]. We have used a Kaufman ion source to study the low energy ion effects during the MBE growth of GaN on sapphire substrates and GaN templates, comparing the results to these models. From a macroscopic point of view our measurements on GaN show quantitative agreement with the curvature driven theories. In particular we use the cross-over between Ga-limited growth and N-limited growth to estimate the N adatom concentration, a key ingredient of the theory. From a microscopic view, however, our RHEED and AFM studies have observed step debunching of multilayer steps and the elimination of hillock spirals. In these measurements, the starting GaN(0001) templates had 20 layer high mesas. After growth, round, nanoscale dimple structures, ranging from 90 nm to 850 nm, with bilayer steps were produced. This was seen with both Ar and nitrogen ions at energies ranging from 100-1200 eV. The size of the dimples and the terrace length of the debunched steps decrease with increasing sample temperature. After ion assisted growth, islands are found at the edges of the debunched steps. By tuning the ion energy and growth rate, uniform distributions of GaN nanoparticles, with means ranging from 50 nm to 200 nm, can be prepared. By combining ion induced step debunching and growth, step flow growth at the debunched steps is obtainable. Partially supported by the NSF and the AFOSR. @FootnoteText@ 1. R. M. Bradley and J. M. E. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988). 2. J. Kim, D. G. Cahill, and R. S. Averback, Phys. Rev. B 67, 045404 (2003).