AVS 60th International Symposium and Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThA

Invited Paper EM2-ThA6
Electronic and Lattice Dynamical Properties of II-IV-N2 Semiconductors

Thursday, October 31, 2013, 3:40 pm, Room 101 B

Session: Non-traditional Inorganic Semiconductors
Presenter: W.R. Lambrecht, Case Western Reserve University
Authors: W.R. Lambrecht, Case Western Reserve University
A. Punya, Case Western Reserve University
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An overview will be presented of our recent results on the electronic band structures and lattice dynamical properties of the II-IV-N2 semiconductors. The electronic band structure of ZnSiN2, ZnGeN2, ZnSnN2 and CdGeN2 were obtained using the quasiparticle self-consistent GW approximation using the full-potential linearized muffin-tin orbital method for the orthorombic wurtzite based structure. They are found to span band gaps from the red to the UV with CdGeN2 having a gap in the green region of the spectrum. Zero point motion corrections of the band gap were estimated as well as exciton binding energies. Comparisons with experimental data are discussed. We also studied the band structure of ZnSnN2 in a few alternative structures and find that the gap can be strongly reduced if besides tetrahedrons of two Zn and two Sn, also tetrahedrons with 1 Zn and 3 Sn or vice versa occur. The splittings of the valence band maximum and the effective masses and generalized Kohn-Luttinger parameters were determined. Spin-orbit splittings are found to be very small. The band offsets between ZnGeN2, ZnSnN2, GaN and ZnO were calculated from interface calculations for different interfaces and indicate an interesting type-II alignment between ZnGeN2, GaN and ZnO. The vibrational spectra were obtained using density functional perturbation theory in a previous series of papers. Infrared and Raman spectra were predicted and compared with the available experimental data. In ZnGeN2 besides the expected peaks for first-order allowed Raman, some additional features are seen in the experimental spectra. We show that these can either be due to disorder induced Raman scattering or to forbidden LO modes and further experimental work using resonant Raman spectroscopy would be useful to distinguish between the two cases. Preliminary results on native point defect calculations will be presented. The difference in energy of formation of the Ge3N4 and Sn3N4 changes the allowed window for chemical potentials of Zn and Ge or Sn. These in turn may have an important effect on the dominant point defects. The prospects for p-type doping are given particular attention. ZnGe antisites, VZn and VGe are all three found to behave as acceptors while GeZn and VN are donors. The relative stability of Ge3N4 together with the requirement to stay on the N-rich line, implies that one cannot make the samples very Ge-rich. This is however favorable for doping Ga on Ge sites which is a potential route to effective p-type doping.