| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Friday Sessions |
| Session EM+NS+SS+TF-FrM |
| Session: | Growth and Characterization of Group III-Nitride Materials |
| Presenter: | C.R. Eddy, Jr., U.S. Naval Research Laboratory |
| Authors: | C.R. Eddy, Jr., U.S. Naval Research Laboratory N. Nepal, American Association for Engineering Education N.A. Mahadik, U.S. Naval Research Laboratory L.O. Nyakiti, American Association for Engineering Education S.B. Qadri, U.S. Naval Research Laboratory M.J. Mehl, U.S. Naval Research Laboratory J.K. Hite, U.S. Naval Research Laboratory |
| Correspondent: | Click to Email |
The synthesis of III-nitride semiconductors by atomic layer epitaxy (ALE) is explored to reveal that growth temperatures for high-quality crystalline layers are less than half that of conventional growth methods and that the new parameter space can lead to previously unrealized phases and stoichiometries of III-N binaries and ternaries.
ALE is a method in which the precursors for growth are introduced in a sequence of gas pulses added to an inert carrier gas flow at temperatures sufficient to promote either homo- or hetero-epitaxial growth. Here, we use alternating pulses of traditional group III metalorganics and plasma-activated nitrogen carried on an ultra-high purity argon carrier gas. A variety of substrates (silicon, sapphire, GaN templates on sapphire, etc.) are subjected to the pulse sequences at temperatures from 150°C to 500°C in a customized Cambridge Nanotech, Inc. Fiji plasma-assisted ALD reactor.
With proper surface preparations, high quality, wurtzitic AlN is grown at 500°C. These thin films (~36 nm) demonstrated smooth surfaces (~0.7 nm rms roughness for 10x10 mm2 scan area) and a (0002) peak rocking curve width of 630 arc-sec [1,2], but contained a high fraction of carbon (8%) and small fraction of oxygen (0.6%). Similar results are demonstrated for GaN films grown between 350 and 450°C. For InN, two growth regimes were defined. One between 175 and 185°C, in which a new cubic phase of InN was realized, and a second regime between 220 and 260°C for which quality wurtzitic materials (262 arc-sec for (0002) reflection) were grown. As with AlN, both films contained high fractions of carbon (3%), but little-to-no oxygen (0.1%). Finally, initial efforts to grow ternaries of InAlN were conducted using a digital alloying approach where quality, crystalline ternaries were realized over the entire stoichiometric range. These early results suggest great potential for ALE growth of III-N semiconductors.
[1] T. Koyama et al., Phys. Stat. Sol. (a) 203, 1603 (2006). MBE (1.58 micron, 420 arc-sec).
[2] K. Balakrishnan et al., Phys. Stat. Sol. (c) 3, 1392 (2006). MOCVD (2 micron, 400 arc-sec).