AVS 45th International Symposium
    Selected Energy Epitaxy Topical Conference Thursday Sessions
       Session SE-ThM

Invited Paper SE-ThM7
Low-Energy Electron Microscopy of (0001) Surfaces of GaN Films@footnote 1,2@

Thursday, November 5, 1998, 10:20 am, Room 327

Session: In Situ Characterization and Real-Time Diagnostics of Surface Growth Processes
Presenter: M.G. Lagally, University of Wisconsin, Madison
Correspondent: Click to Email
The ability to observe growth in real space and in real time at growth temperatures and manipulate growth conditions dynamically is essential to determine fundamental mechanisms of epitaxial growth, especially in complex systems. Only low-energy electron microscopy (LEEM) provides this capability. We have begun a program of LEEM investigations of the surfaces of GaN films prepared in several ways as a springboard to subsequent in-situ exploration of homoepitaxial growth. Surfaces of films grown by metal-organic vapor phase epitaxy (MOVPE), by halide vapor phase epitaxy (HVPE), and by lateral epitaxial overgrowth (LEO) using MOVPE are compared. Although a number of surface reconstructions have been observed, clean stoichiometric GaN(0001) surfaces are unreconstructed, and hence conventional dark-field imaging cannot provide information on terrace sizes and step heights, although steps themselves can be viewed with step-contrast imaging. We demonstrate that through use of multiple scattering we can view terraces and step heights and determine terrace size distributions. We compare surface morphologies of the above films. We have also demonstrated (so far only on SiGe/Si) that LEEM has potential for imaging 3D features. We have identified 3D epitaxial islands and have followed in real time their shape and size evolution during embedding by matrix material. We will describe initial LEEM measurements of Ga deposition on the above GaN surfaces as a start to homoepitaxial growth. Although none of this work as yet reflects selected-energy epitaxy, it will help to establish the baseline for understanding growth mechanisms that might be modified by selecting the energies of the depositing species. @FootnoteText@ @footnote 1@Research supported by ONR. @footnote 2@Work done in conjunction with J. Maxson, L. Zhang, T. Kuech, and P. Sutter.