AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThM

Paper SS3-ThM8
First Principles Study of Cross-sectional Surface Structure of III-V Heterostructures

Thursday, October 5, 2000, 10:40 am, Room 210

Session: Surface and Interface Structure II
Presenter: S.-G. Kim, Vanderbilt University
Authors: S.-G. Kim, Vanderbilt University
S.C. Erwin, Naval Research Laboratory
B.Z. Nosho, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
Heterostructures of III-V semiconductors form the basis for a variety of devices. The performance of these multilayer structures is extremely sensitive to the thickness of the layers and the nature of the interfaces between them. As the layers are made thinner, a microscopic understanding of interface structure and chemistry will become increasingly important for optimizing device performance. The challenge is how best to achieve a complete microscopic characterization. We demonstrate the power of combining density-functional theory with experimental data from cross-sectional scanning tunneling microscopy (XSTM). We use first-principles computational methods to interpret XSTM images that we have obtained from the (110) cleavage surface of 6.1-Å III-V heterostructures. We begin by determining theoretically the fully relaxed geometry of cleaved InAs/GaSb superlattices, using the local-density approximation (LDA) to density-functional theory. To understand the relative importance of electronic vs. structural effects in the STM topography, we generate simulated XSTM images over the cross-sectional surface and compare with our measured XSTM images. We also focus on the role played by the specific interface bond type (In-Sb vs. Ga-As bonds) and show, for example, that XSTM can indeed be used reliably to identify the interface bond type. Finally, we study in detail the thermodynamics of defect formation due to diffusion across the interface; these theoretical predictions compare very favorably with our XSTM studies, and form the basis for further studies of the impact of interfacial disorder on device performance.