Exploring Solute Distribution and Clustering in GaAsBi and GaAsNBi Alloys Using Local- Electrode Atom Probe Tomography

Due to the significant bandgap narrowing induced by the incorporation of dilute fractions of N and Bi into compound semiconductors, emerging dilute nitride-bismide alloys are of significant interest for optoelectronic devices operating in the near- to mid-infrared range. Previously, using direct measurements of N and Bi mole fractions via ion beam analysis, in conjunction with direct measurements of the out-of-plane misfit via x-ray rocking curves, we found the “magic ratio” for lattice-matching of GaAsNBi alloys with GaAs substrates. Here, we use local-electrode atom probe (LEAP) tomography to measure the stoichiometry to determine if isovalent co-alloying of GaAs with two anions (Bi, N) is limited to the replacement of As by the anions. We find that LEAP using low laser energy provides optimal conditions for probing the stoichiometry in GaAsNBi specimens. Using this data, we explore correlations between the microstructure and local electronic states, and in particular, the influence of metallic clustering. To determine the structure-property relationships, cluster analysis will be conducted on Bi atoms within the films and band structures will be calculated using the local Bi and N data as input into self-consistent Schrodinger-Poisson simulations.