Paper EM-ThM12
Atomistic Analysis of Ge on a-SiO2 using an Emipirical Interatomic Potential to Describe Selective Epitaxial Growth
Thursday, November 1, 2012, 11:40 am, Room 009
Integration of Ge and III-V compound semiconductors on Si has received significant recent attention for the next-generation, high-mobility transistors and III-V optoelectronic and photovoltaic devices.[1] However, managing dislocations and film stress due to lattice mismatch and thermal expansion coefficient mismatch remains a significant engineering challenge. One possible solution is selective epitaxial growth (SEG) where the epitaxial layer is grown in select areas to simultaneously manage dislocations and stress. For SEG, a dielectric layer (e.g., SiO2 and Si3N4) with open windows that expose the underlying Si is typically employed to reduce the contact area between the deposited epitaxial layer and Si substrate, resulting in lower mismatch stress and defect density.[2] The selectively grown epitaxial islands can be further grown laterally over the dielectric layer and coalesced into a continuous film. The SEG technique squarely relies on weak interaction between growth precursors and the dielectric film, which prevents random nucleation. For instance, we have previously reported that desorption and surface diffusion barriers of Ge adspecies on SiO2 are 0.44 ± 0.03 and 0.24 ± 0.05 eV, respectively.[3, 4] Herein, we present an atomistic analysis of Ge on SiO2 in order to validate a Tersoff-based model for Si-Ge-O [5, 6]. We compare simulation predictions to detailed experimental data for a variety of properties. In particular, we consider bulk SiO2 structural parameters as a function of temperature, Si-SiO2 and Ge-SiO2 interface energies, and the Ge-on-SiO2 desorption energy and diffusion behavior. We show that with a single fitting parameter, the potential model provides a good overall description of the Si-Ge-O system, while retaining the highly efficient nature of the Tersoff potential, making it a good choice for larger-scale atomistic studies of Ge-on-Si SEG. We conclude by showing example calculations of stress distributions in epitaxial Ge islands in an SEG system.
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