AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM1-TuM

Invited Paper EM1-TuM1
The Role of Defects at Nanoscale Semiconductor Interfaces

Tuesday, November 1, 2005, 8:20 am, Room 310

Session: Defects, Interfaces, and Surface Passivation in Electronic Materials
Presenter: Y.M. Strzhemechny, The Ohio State University
Authors: Y.M. Strzhemechny, The Ohio State University
H.L. Mosbacker, The Ohio State University
M.J. Hetzer, The Ohio State University
M. Gao, The Ohio State University
B.D. White, The Ohio State University
D.C. Look, Wright-Patterson AFB
D.C. Reynolds, Wright-Patterson AFB
C.W. Litton, Wright-Patterson AFB
M.A. Contreras, National Renewable Energy Laboratory
A. Zunger, National Renewable Energy Laboratory
L.J. Brillson, The Ohio State University
Correspondent: Click to Email
Current understanding and control of semiconductor contacts increasingly require measurements sensitive to defects and chemical changes at nanoscale interfaces. We offer examples illustrating dramatic macroscopic effects occurring in semiconductor systems as a result of nanoscale interface phenomena. In some cases, there is an interplay of several competing defect-driven mechanisms. Elucidating them and finding the leading ones requires careful experimental approach. For single-crystalline ZnO, we study the role of near-surface defects on the formation of Au Schottky contacts. Among factors degrading rectifying characteristics of such contacts one should consider the following. High concentrations of shallow donors in the surface and subsurface regions lead to barrier thinning, resulting in increased tunneling. Alternatively, the presence of deep defects near contact interface promotes tunneling by defect-assisted hopping. Nanoscale electronic and chemical studies show that independent reduction of both shallow donors and deep defects significantly improves rectifying performance of the Au/ZnO contacts. We find that processing of ZnO with remote O and H plasma allows for controllable tailoring of chemical and physical properties of the surface. By the same token, nanoscale compositional and electrostatic variations between grain boundaries and grain interiors in thin polycrystalline films of Cu(In,Ga)Se@sub 2@, absorber layers in record-setting solar cells, show how nanoscale arrangement of near-surface stoichiometric defects may improve the overall photovoltaic efficiency. Confirming theory, we find a 50% reduction in Cu composition from grain interior to boundary and a p-type potential barrier that acts to reduce majority carrier hole recombination. These and related examples emphasize the practical significance of nanoscale chemical and electronic features at electronic material interfaces.