| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM2-ThA |
| Session: | Non-traditional Inorganic Semiconductors |
| Presenter: | N. Feldberg, University at Buffalo |
| Authors: | N. Feldberg, University at Buffalo J.D. Aldous, University at Buffalo W.M. Linhart, University of Liverpool, UK T.D. Veal, University of Liverpool, UK P.A. Stampe, Florida A&M University R.J. Kennedy, Florida A&M University D.O. Scanlon, University College London, UK L.F.J. Piper, Binghamton University L. Schweidenback, University at Buffalo A. Petrou, University at Buffalo S. Durbin, University at Buffalo |
| Correspondent: | Click to Email |
Over the past decade indium has experienced significant price fluctuations due to limited supply and increasing demand; these factors have motivated the search for alternative semiconductor materials based on earth-abundant elements. Such materials should still have a direct tunable bandgap similar to existing indium-containing semiconductor compounds. One candidate which may exhibit these desirable properties is ZnSnN2. In addition to the abundance and low price of the constituent elements, Zn and Sn benefit from a well-established recycling infrastructure. Little is known about the properties of this material, however it is predicted to have a band gap near 2.0 eV. This band gap should be tunable through alloying with either wider or narrower band gap members of the Zn-IV-N2 family, making it attractive for a range of optoelectronic device applications. The crystal structure of ZnSnN2 is derived from that of InN through an ordered substitution of Zn and Sn on the In sublattice. The resulting structure is predicted to be orthorhombic due to the different metal-N bond lengths distorting the wurtzite structure of InN.
A series of ZnSnN2 films have been grown via plasma-assisted molecular beam epitaxy (PAMBE) on (111)-oriented yttria-stabilized zirconia and LiGaO2(001) substrates. Regardless of substrate type and growth conditions, all films exhibit a monoclinic structure based on x-ray diffraction (XRD) and supported by reflection high energy electron diffraction (RHEED). The crystallization in a monoclinic structure can be explained by the existence of a disordered cation sublattice. Similar lattice arrangements have been observed to occur in related compounds ZnGeN2 [1] and ZnSnP2 [2] in the presence of varying degrees of cation ordering. We have found that growth of high quality single crystal epitaxial films is dependent on having a high Zn:Sn flux ratio. Single crystal films were observed for flux ratios in excess of 20:1. The need for such an extremely large overpressure of Zn is expected due to the significant difference in vapor pressures between Zn and Sn. Hall effect and optical absorption suggest a variation in band gap energy as a function of crystal quality beyond expectations for Moss-Burstein and band gap renormalization effects, which is consistent with density functional theory predictions.
This project is supported by NSF grant DMR1244887 (Program Director Charles Ying), and EPSRC grant EP/G004447/2 .
1. 1. W. R.L. Lambrecht, E. Alldredge, and K. Kim, Phys. Rev. B 72 (2005) 155202.
2. D.O. Scanlon and A. Walsh, Appl. Phys. Lett. 100 (2012) 251911.