Paper EM1-MoA4
The Effect of Ammonia - TMI Pulse Separation on the Structural Properties of InN Epilayers
Monday, October 31, 2011, 3:00 pm, Room 209
| Session: |
Group III-Nitrides and Hybrid Devices |
| Presenter: |
Ramazan Atalay, Georgia State University |
| Authors: |
R. Atalay, Georgia State University
M. Buegler, Technische Universität Berlin, Germany
S. Gamage, Georgia State University
I. Senevirathna, Georgia State University
A.G.U. Perera, Georgia State University
J.S. Tweedie, North Carolina State University
R. Collazo, North Carolina State University
N. Dietz, Georgia State University
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| Correspondent: |
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Over the last decade, significant research efforts have been devoted to understand and improve the properties of InN epilayers. However, even today, there is a significant lack of on understanding of the InN surface and growth chemistry and its affect on the physical bulk properties. Crucial challenges in the growth of InN epilayers are the vast different partial pressures between indium and nitrogen and associated fragments of the utilized precursors trimethylindium (TMI) and ammonia (NH3).
In this work, high-pressure chemical vapor deposition (HPCVD) is employed and explored in order to control and suppress the disassociation of InN alloys at higher growth temperatures. In order to reduce gas phase reactions and to control the surface chemistry, a pulsed precursor injection approach has been implemented, which provides additional process control parameters for the optimization of the physical epilayers properties.
In the pulsed precursor injection approach, the precursor separation times between the metal organic (MO) sources (TMI and TMG) and ammonia (S1), and ammonia and MO (S2) are two critical process parameters.
This contribution will present results on how the precursor separation times between the TMI and ammonia (S1) and ammonia and TMI (S2) affect the structural and optical properties of InN epilayers grown on GaN/sapphire templates and/or sapphire substrates. In this study, the separation times S1 and S2 have been varied from 1000 to 2500 ms and 250 to 500 ms, respectively. The results show that a longer S1 separation of around 1700 ms and short S2 separation of around 360 ms provide the best structural properties of InN epilayers.
The InN epilayers have been analyzed by Raman scattering, X-ray diffraction, IR reflection, and transmission spectroscopy. The Raman studies showed that the lowest FWHM of E2(high) vibrational mode with about 8 cm-1 for a S2 separation time of 358 ms. XRD 2Θ-ω scans on these InN epilayers and the analysis of the InN (0002) Bragg reflex confirm the improved structural properties for the optimized S2 separation.