Atomic-Scale Tracking of Dopant Atoms

University Of Arkansas, Fayetteville AR

Investigators

Abstract

Technical: The doping of semiconductors is a cornerstone of the electronics industry. This project focuses on using surface properties to aid low-solubility dopant atoms in finding the desired place in the host crystal lattice. The specific material system studied in this project is Mn-doped GaAs, which has potential for spintronics applications. The experiments include growth of semiconductor materials using molecular beam epitaxy (MBE) and surface diffusion studies using scanning tunneling microscopy (STM). The central idea of project is to utilize the various configurations of GaAs(001) surface to find a natural way for Mn dopant atoms added to the surface to end up in substitutional positions in favor of interstitial positions. Surfaces, unlike the bulk, offer a rich variety of stable configurations and each one can be independently formed across the entire surface thereby providing many unique and chemically varied templates for aiding the doping process during layer-by-layer growth. Specifically, some surfaces are arsenic rich, some are gallium rich, some have a symmetric geometry, some have an asymmetric geometry, some are free of edge sites and others a full of edge sites, and so on. In order to fully understand the non-equilibrium (kinetic) doping process at the atomic-scale, this project aims to study the entire pathways of the dopant atom from initial deposition onto a surface to its final bulk bonding site. In doing this, the doping processes will be uncovered and quantified via the diffusion coefficients, energy barriers, diffusion anisotropies, and the sticking anisotropies. Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. The science involved in this research project will impact the field of impurities in semiconductors. Graduate and undergraduate students will be trained for semiconductor growth, scanning tunneling microscopy characterization, vacuum techniques, as well as all phases of scientific research such as literature research, presentation skills, and writing refereed journal articles. A creative outreach activity of this project is hosting of Girl and Boy Scouts in the PI's research laboratory, where the children build atomic models, spot weld, and study different vacuum environments.