Ion Beam Analysis of Solute Incorporation in GaAsN and GaAsNBi Alloys

Highly mismatched alloys (HMAs) consist of highly immiscible solute atoms in a solvent. In dilute nitride semiconductor alloys, due to the resonant interactions between the conduction and/or valence band of the solvent and energy levels of the N solute, the bangdgap energies can be tuned dramatically without a significant change in lattice parameter, making them promising for a wide variety of optolelectronic applications. However, it has been shown that post-growth rapid thermal annealing (RTA) is needed to achieve suitable transport properties and emission efficiencies. Therefore, identification of the local atomic environments of the N solute atoms and the influence of RTA and anion co-incorporation on those environments is needed. In the case of GaAsN, several groups have suggested that N shares an arsenic site with either arsenic or another N atom, often termed (N-As)As or (N-N)As split interstitials. To distinguish (N-N)As and (N-As)As interstitials in GaAsN alloys, we compare nuclear reaction analysis (NRA) spectra with simulations utilizing full numerical integration of ion trajectories. In both cases, incident particle paths along the [100], [110], and [111] directions are considered. Both the measured and simulated channeling NRA spectra exhibit the highest (lowest) yields in the [111] ([100]) directions, suggesting that dominant interstitial complex is (N-As)As. In addition, we use our combined computational-experimental approach to examine the influence of rapid-thermal annealing (RTA) on the local environment of N atoms, identifying a plausible mechanism for dissociation of (N-N)As into Nsub and (N-As)As. For GaAsN and related alloys, co-alloying with larger group V elements such as Sb or Bi is expected to lead to significant energy bandgap narrowing using a substantially lower N fraction, and a correspondingly lower concentration of N-related defects that degrade carrier mobilities and optical efficiencies. For GaAsNBi, the published experimental work has focused primarily on growth parameters and optical properties, without addressing the mechanisms for N and Bi co-incorporation during epitaxy. The incorporation of Bi is found to be independent of N flux, while the total N incorporation and the fraction of N atoms occupying non-substitutional lattice sites increase with increasing Bi flux. In addition, a comparison of channeling nuclear reaction analysis along the [100], [110], and [111] directions with Monte Carlo-Molecular Dynamics simulations indicates that the non-substitutional N primarily incorporate as (N-As)As interstitial complexes. Finally, we determine the “magic ratio” for lattice matching of GaAsNBi to GaAs: [Bi]≈(1.23±0.04)[N].PHDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/140830/1/timyjen_1.pd