AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThM

Paper EM-ThM4
The Surface Structures of In@sub x@Ga@sub 1-x@As@sub y@P@sub 1-y@ (001) Films Grown by Metalorganic Vapor-Phase Epitaxy

Thursday, November 5, 1998, 9:20 am, Room 316

Session: Compound Semiconductor Surface Chemistry
Presenter: L. Li, University of California, Los Angeles
Authors: L. Li, University of California, Los Angeles
B.-K. Han, University of California, Los Angeles
M.J. Bergarney, University of California, Los Angeles
D. Law, University of California, Los Angeles
Q. Fu, University of California, Los Angeles
R.F. Hicks, University of California, Los Angeles
Correspondent: Click to Email
Strained films of In@sub x@Ga@sub 1-x@As@sub y@P@sub 1-y@ were grown on GaAs and InP (001) substrates by metalorganic vapor-phase epitaxy (MOVPE). The film thickness and composition, and the degree of strain were determined by analysis of high-resolution x-ray diffraction spectra. In addition, the large-scale morphology, the atomic structure and the composition of the film surfaces were characterized after growth by low-energy electron diffraction, x-ray photoelectron spectroscopy, infra spectroscopy of adsorbed hydrogen, and scanning tunneling microscopy. All the surfaces immediately following MOVPE are composed of atomically flat terraces that are separated by double height steps. The steps exhibit smooth, gradual undulations along the terrace edges. Close-up images of the terraces reveal a disordered (2x1) or c(4x4) structure, which arises from a random mixture of group V atoms and alkyl groups adsorbed on top of the surface. Annealing in vacuum desorbs the alkyl groups and then the group V atoms, generating a variety of reconstructions at progressively higher group III coverages. Many new reconstructions are observed on these films, including (2x3), (3x2) and other (nx2) unit cells, where n is an odd integer. Evidently, these surfaces do not obey the electron counting scheme that holds for unstrained GaAs (001), and therefore, they may be positively or negatively charged. The structure and properties of some of these new surfaces will be described at the meeting.