| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
II4, Characterization of Lateral and Vertical Inhomogeneities in InAlN Grown by Plasma-Assisted Molecular Beam Epitaxy |
| Author(s) |
Wei Kong, Wenyuan Jiao, Tongho Kim, Maria Losurdo, Giovanni Bruno, April Brown |
| On-Site Speaker (Planned) |
Wei Kong |
| Abstract Scope |
Lattice-matched In0.17Al0.83N/GaN is of substantial interest for III-N device applications. For electronic devices, the high spontaneous polarization of InAlN enables high electron concentrations. However, the growth of device-quality InAlN by molecular beam epitaxy (MBE) is still challenging because of the inability to achieve high growth temperature due to In desorption and consequent low mobility of Al on the evolving surface at the limited growth temperatures. Recent TEM studies have identified the presence of a nanoscale columnar structure in InAlN grown by MBE resulting from a platelet coalescence layer-by-layer growth mode. MOCVD-grown InAlN films, in comparison, are laterally uniform. Therefore, the characterization of both the vertical and lateral compositional uniformity in PAMBE grown InAlN films is critical in order to ultimately understand and control the relationships between growth conditions and optical and electrical properties. In this report, we present our investigation on the lateral and vertical inhomogeneities observed in InAlN grown by PAMBE near the lattice-matched composition to GaN. A series of InAlN films were grown on GaN templates at the temperature from 400℃ to 540℃ under N-rich and stoichiometric conditions. These films show a smooth micron-scale morphology (RMS of 0.3nm as determined by atomic force microscopy (AFM)). Reciprocal space map (RSM) characterization indicates that all samples are pseudomorphic with In content from 14%~17%. However, x-ray diffraction rocking curve fitting indicates that several samples possess two compositional regions with an In-poor layer nearest to the surface. The thickness of the In-poor layers varies from 2nm~5nm with In content of 5%~10%. The vertical inhomogeneity is to be compared to that observed for InGaN heterostructures which are widely reported to be capped by an In-rich layer. In addition, we investigated the characterization of the lateral inhomogeneity of InAlN layers by observing the variation of RSM intensities for a given sample. The ratio for the layer peak to the substrate peak decreases from that for the (002) plane to the (105) plane, which indicates an anisotropic deterioration of crystalline quality. Compared to the same characterization applied to InGaN samples, the effect is much less significant. Such inhomogeneities in InAlN can be introduced by the presence of V-defects penetrating from the substrate to the InAlN surface as identified by AFM and scanning electron microscopy (SEM). In addition, the nanoscale columnar structure will also introduce such asymmetry. |
| Proceedings Inclusion? |
Undecided |