Structural properties of InN films grown in different conditions by metalorganic vapor phase epitaxy
- PDF / 189,720 Bytes
- 6 Pages / 584.957 x 782.986 pts Page_size
- 27 Downloads / 221 Views
N thin films were grown on GaN underlayer with sapphire substrate by metalorganic vapor phase epitaxy under different growth conditions, including growth temperature, reactor pressure, and V/III ratio. X-ray diffraction and Raman scattering measurements reveal that the samples grown at different temperatures are mixed with different phases, especially at higher temperature. The calculated phonon dispersion curves of wurtzite, zinc-blende, and rocksalt structures show that the samples mainly contain wurtzite structure and small amount of zinc-blende phase, while the samples grown at 600 °C and 650 °C include a new structural phase other than the three well-known ones. This analysis demonstrates that the InN epilayer grown at 550 °C has the highest phase purity and better crystalline quality. Besides the key role of growth temperature, a relatively higher reactor pressure and lower V/III ratio are found to be more conducive to the improvement of crystalline quality, though they have a modest effect on the InN microstructure.
I. INTRODUCTION
In recent years, there has been a sustained interest on III-nitrides driven by their wide-range band gaps suitable for optoelectronics applications especially in near-IR/ near-UV devices. Among all the III-nitrides, InN has the shortest direct band gap1,2 and smallest effective mass for electrons,3 which leads to high mobility and high saturation velocity at room temperature. These advantages make it a highly competitive candidate for various optoelectronic devices, such as solarcell, high mobility transistors, light-emitting diodes, and so on.4 The growth of single crystalline and good quality InN films has been widely studied since the 1990s by metalorganic vaporphase epitaxy (MOVPE). Because of the low InN dissociation temperature and extremely high equilibrium vapor pressure of nitrogen over the InN film,5 a low-growth temperature of about 500 °C is necessary for InN preparation. However, this work is extremely challenging due to a low decomposition rate of NH3 at low-growth temperature, which restricts the achievement of high quality InN films. Therefore, the knowledge on the fundamental properties, such as the structural, electrical, and optical properties, of InN material is of shortage. In this work, a series of InN films were grown in different conditions using MOVPE to understand their structural properties. The crystalline structures of asgrown wafers were analyzed by x-ray diffraction (XRD) and Raman scattering measurements. Moreover, a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2010.87 J. Mater. Res., Vol. 26, No. 6, Mar 28, 2011
http://journals.cambridge.org
Downloaded: 27 Mar 2015
phonon dispersions were simulated by the first principles calculation to identify the experimental results. The relationship between the structural properties of InN films and growth conditions is systematically discussed. II. EXPERIMENTAL AND THEORETICAL DETAILS
A series of nominally undoped InN films were epitaxied on a 1.5-lm-thick wurtzite GaN u
Data Loading...
