| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM+NS-ThA |
| Session: | Wide and Ultra-wide Band Gap Materials for Electronic Devices: Growth, Modeling, and Properties |
| Presenter: | Amber Reed, Air Force Research Laboratory |
| Authors: | A.N. Reed, Air Force Research Laboratory H.A. Smith, Air Force Research Laboratory D.C. Abeysinghe, Air Force Research Laboratory P.J. Shah, Air Force Research Laboratory L. Grazulis, Air Force Research Laboratory M.J. Hill, Air Force Research Laboratory M.E. McConney, Air Force Research Laboratory B.M. Howe, Air Force Research Laboratory A.M. Urbas, Air Force Research Laboratory |
| Correspondent: | Click to Email |
High temperature stability, hardness, abrasion resistance, chemical stability and potential complimentary metal-oxide semiconductor process compatibility, combined with a high electrical conductivity make titanium nitride (TiN) an important material for electronic and opto-electronic applications. TiN is particularly important as an electrode material due to its oxidation resistance, which can be improved by alloying it with aluminum nitride to form titanium aluminum nitride (Ti1-xAlxN). In addition to its use as an electrode, TiN is also a promising plasmonic material because, similar gold, it possesses a zero crossover wavelength in the visible region. The ability to synthesize high quality TiN crystals on different electronic substrates would greatly facilitate its incorporation in electronic and opto-electronic devices. One particular material of interest is lithium niobate (LiNbO3), which possesses unique piezoelectric, opto-electronic and nonlinear optical properties. Synthesis of high quality TiN on LiNbO3 would allow for integration of TiN into acoustic devices (i.e. SAWs and BAWs), optical modulators, and other electronic and opto-electronic devices.
In this work, we demonstrate the synthesis of high quality epitaxial TiN crystals on Z-cut LiNbO3 substrates. We also discuss the growth of TiN and Ti1-xAlxN on Y-cut LiNbO3. While the (001) plane of Z-cut LiNbO3 creates a template for epitaxial growth of (111)-oriented TiN crystals, similar to growth on (001)-oriented sapphire, the (010) plane of Y-cut LiNbO3 is equally lattice matched to the TiN (001) and (101) planes which results in competitive growth of those two orientations. Alloying the TiN with AlN exacerbates this issue as the lattice constant shrinks with increased AlN content. We investigate the role of deposition power, nitrogen gas fraction, and substrate temperature and ion flux impingement on the competitive growth to determine the optimal growth conditions to promote epitaxy. Films are characterized using x-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy, ellipsometry and electrical measurements. XRD and AFM of TiN on Z-cut LiNbO3 show remarkably smooth (< 220 pm RMS roughness) epitaxial films. Ellipsometry measurements of the TiN on Z-cut LiNbO3 reveal carrier concentrations up to 4.0 x1022 cm-3, mobilities of ~3.2 cm2/(V s) and a ε1/ ε2 of 1.00 to 3.34 at a wavelength of 1550 nm.