Electronic Materials (Prof. Morgan)

Defects in semiconductors are critical to controlling their electronic transport properties. We have developed newly accurate of models of defect cluster stability and transport in ZnO[15, 16], predicting Fermi level dependent mobility for the intriguing As-2Vac clusters in this system. We are also developing models for growth of Bi doped GaAs systems, of great interest for their ability to provide band gap and lattice parameter matching for laser and telecommunications applications. We are establishing Bi thermodynamics[17] and kinetics to predict how the far from equilibrium incorporation of Bi is enabled by low growth temperatures and how growth conditions and alloying elements can be used to enhance Bi incorporation while maintaining high film quality.

[15] B. Puchala and D. Morgan, Stable interstitial dopant-vacancy complexes in ZnO, Physical Review B 85 (2012).
[16] B. Puchala and D. Morgan, Atomistic modeling of As diffusion in ZnO, Physical Review B 85 (2012).
[17] H. Jacobsen, B. Puchala, T. F. Kuech, and D. Morgan, Ab initio study of the strain dependent thermodynamics of Bi doping in GaAs, Physical Review B 86 (2012).


Fig.6: The (a) effective activation energy, and (b) effective diffusivity of As vs. Fermi level, both under O-rich conditions.  Separate lines are plotted in both (a) (though they fall on top of each other) and (b) for temperatures ranging from 300-1300 K at intervals of 100 K. Regions (1)–(3) in (a) correspond to diffusion being predominately by AsI,oct, AsZn-1VZn, and AsZn-2VZn, respectively, while AsZn is the most prevalent As-containing species.  Region (4) corresponds to AsZn-2VZn dominating diffusion and being the most prevalent As containing species.  From Ref. B. Puchala and D. Morgan, Atomistic modeling of As diffusion in ZnO, Physical Review B 85 (2012).