| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF+SA+MI-TuM |
| Session: | Thin Films for Synchrotron and Magnetism Applications |
| Presenter: | Neeraj Nepal, US Naval Research Laboratory |
| Authors: | N. Nepal, US Naval Research Laboratory V. Anderson, US Naval Research Laboratory S.D. Johnson, US Naval Research Laboratory D.J. Meyer, US Naval Research Laboratory B.P. Downey, US Naval Research Laboratory A.C. Kozen, US Naval Research Laboratory Z.R. Robinson, SUNY College at Brockport D.R. Boris, US Naval Research Laboratory S.C. Hernández, US Naval Research Laboratory S.G. Walton, US Naval Research Laboratory K.F. Ludwig, Boston University C.R. Eddy, Jr., US Naval Research Laboratory |
| Correspondent: | Click to Email |
III-N semiconductors have found application in a variety of technologies such as high power transistors, emitters, detectors, and solar-cells. The relatively high growth temperature of common III-N synthesis techniques has impeded further development and application of the materials due to challenges with miscibility gaps and strain related to thermal expansion mismatch with non-native substrates. To address these challenges, Plasma assisted atomic layer epitaxy (PA-ALE) offers a new approach to low temperature III-N growth and can be used to epitaxially grow InN by using alternative pulses of trimethylindium and nitrogen plasma [1]. Since growth using this technique is far from thermodynamic equilibrium, understanding how nitrogen plasma affects nucleation and growth kinetics is essential for development.
Real-time grazing incidence small angle x-ray scattering (GISAXS) measurements at the Cornell High Energy Synchrotron Source were used to study the effect of variation in nitrogen plasma pulse conditions on PA-ALE of InN at 250 °C. Current results show the evolution of GISAXS characteristics such as the correlated peak (CP) length scale in the Yoneda Wing (YW) directly relates to the surface roughness, impurities, and electrical properties of the material. During the initial cycles of InN growth, the diffuse specular reflection broadens and CPs start to evolve along the YW with different correlated length scales. For the nitrogen plasma pulse time (tp) of 15 seconds, the CPs have two different correlated length scales of 33.36 and 8.38 nm. With increasing tp to ≥ 20s (the empirically optimal pulse length), a YW with only one CP evolves and the longest correlated length scale of 11.22 nm is for Tp = 25s. The correlated length scale of this single CP decreases to 10.75 nm for tp = 30s. Additionally at tp = 25s, the growth rate is largest (0.035nm/cycle – consistent with previously reported self-limited growth [1]) with root mean square surface roughness and carbon impurity at or below AFM and XPS sensitivity limits, respectively. The nature of GISAXS CP correlated length scale directly relates to the material quality. GISAXS also shows that the N2/Ar flow ratio significantly affect the nucleation and growth of InN. Based on various ex situ characterization methods, the quality of the PA-ALE grown films is similar or better than the material grown by conventional growth methods, for example, molecular beam epitaxy at higher temperature (>400 °C).
[1] Nepal et al., Cryst. Growth and Des. 13, 1485 (2013).