1. Identifying the Dominant Interstitial Complex in GaAsN Alloys The concentration and local atomic environment of solute atoms determine the electronic properties of semiconductor alloys. In GaAsN, a variety of N atomic configurations have been reported. Here, we use experimental channeling measurements and Monte Carlo-Molecular Dynamic simulation to reveal (N-As) As as the dominant configuration in GaAsN. Rachel S. Goldman, University of Michigan Ann Arbor, DMR 1006835 Sponsored by NSF through DMR- 1006835 (Left): NRA yields and crystal views in [100], [110], and [111] channeling directions for (a) experimental data, (b) GaAs with N sub interstitial, (c) GaAs with (N- N) As interstitial, and (d) GaAs with (N-As) As interstitial and its respective. The yield trends are different for each configuration due to the cross-section view. For example, in (d) [111] the N atom is not shadowed completely by the Ga atom while it is completely shadowed in other configuration, thereby giving higher yields in [111] direction than other two simulated configuration. (Right): Experimental NRA spectra of a GaAsN films in [100], [110], [111] and random channeling directions. The 14 N(d,α 0 ) 12 C and 14 N(d,α 1 ) 12 C reaction energy peaks are identified and the integrated peak counts are caculated and compared. It is found that Y [111] > Y [110] > Y [100]. Counts (Arbitrary Units) Channeling Direction (b) (c) T. Jen, G. Vardar, Y.Q. Wang, R.S. Goldman, “Identifying the Dominant Interstitial Complex in GaAsN Alloys” (to be submitted) (d)

2. Bi Si Ga Si As Mechanisms of dopant incorporation during molecular beam epitaxy of GaAsBi Due to the significant bandgap reduction associated with Bi incorporation, GaAsBi alloys have been proposed for high-efficiency optoelectronic devices. However, to date, the inclusion of GaAsBi alloys in such devices has been hindered by the challenges associated with p-type doping of GaAsBi. Here, we identify the role of the transition from group V-rich to group III-rich conditions, i.e. the stoichiometry threshold in the presence of Bi, on the transition from Si-induced n-type to p-type doping of GaAsBi. Sponsored by NSF through DMR-1006835 Rachel S. Goldman, University of Michigan Ann Arbor, DMR 1006835 Group V-rich: n-type Group III-rich: p-type R.L. Field III, T. Jen, J. Occena, B. Yarlagadda, C. Kurdak, R.S. Goldman, to be submitted Ga As Si Ga As Map of carrier type for growth rate vs. group V/III (beam equivalent pressure) BEP ratio. The group V to group III stoichiometry threshold for GaAsBi is plotted as a dotted line. Inset: Atomic configurations for Si in GaAsBi Scanning electon micrographs (left) and corresponding energy dispersive spectroscopy (right) of GaAsBi films: (top) p-type with Ga droplets, (middle) p-type with droplets removed by HCl etching, and (bottom) droplet-free n-type. Before etching After HCl etching

3. Undergraduate and High School Students in Research Rachel S. Goldman, University of Michigan Ann Arbor, DMR 1006835 Participation in research is a proven way to enhance the quality of education and encourage students to pursue STEM careers. To date, this project has provided research training for a total of 5 graduate, 9 undergraduate, and 5 high school students. All of the students learned about semiconducting materials and their importance for electronic and photonic applications while participating in their projects. In addition, the students learned a combination of various technical skills such as ultra-high vacuum techniques, molecular beam epitaxy, and electron transport measurements. For the past decade, we have solicited substantial involvement of local high school (HS) students in research. Many students have been successful in local and regional science fair competitions. During the past three years, we have expanded the program to involve students and teachers from other HSs. In conjunction with the UM MRSEC, 20 HS students, including 10 from the Ann Arbor/Ypsilanti area, have participated in the residential portion of the “C-PHOM High School Research Program”, established by Goldman. (Top): High School students presenting their research at the UM Summer Undergraduate/High School Student Research Symposium. (Bottom): 2014 C-PHOM High School Research Program participants.