InN Substrates Research Articles

Epitaxial Growth of Thick Polar and Semipolar InN Films on Yttria‐Stabilized Zirconia Using Pulsed Sputtering Deposition

We grew thick InN films on yttria‐stabilized zirconia (YSZ) substrates by high‐growth‐rate pulsed sputtering deposition. X‐ray diffraction analysis revealed that the in‐plane orientation distribution of the InN (0001) films on YSZ decreased as the film thickness increased. The edge dislocation density of the 9.0‐µm‐thick InN film grown at a rate of 6 µm h−1 is calculated to be 1.7 × 109 cm−2, and the atomically flat surface exhibited a step‐and‐terrace structure. In addition, the crystallinity of semipolar InN is improved by increasing the film thickness. These results indicate that high‐growth‐rate pulsed sputtering deposition can be used to prepare InN substrates for the fabrication of high‐speed electron devices and InGaN‐based, long‐wavelength light‐emitting devices.

Synthesis of hexagonal ZnO microdisk on InN substrate by aqueous method and its optical properties

Hexagonal ZnO microdisks were obtained by using InN/sapphire as substrate via the aqueous method. The growth mechanism of the ZnO microdisks was proposed and demonstrated. Moreover, the optical properties of the ZnO microdisks were investigated by micro-photoluminescence, whispering gallery mode (WGM) lasing from the microdisk was observed at moderate excitation density. It will provide a new way to design microlasers by using low temperature method.

Self-assembled InN micro-mushrooms by upside-down pendeoepitaxy

Self-assembly of hexagonal InN micro-mushrooms on Si (111) substrates by molecular beam epitaxy is reported. Scanning electron microscopy (SEM) reveals hexagonal mushroom caps with smooth top surfaces and a step-like morphology at the bottom surface. A detailed growth study along with SEM measurements reveals that an upside-down pendeoepitaxy mechanism underlies the formation of these structures. Cryogenic temperature photoluminescence measurements on the InN disks show a dominant band-to-acceptor recombination peak at 0.68eV. Cross-section annular bright field (ABF-) scanning transmission electron microscopy (STEM) reveals that the growth of these structures occurs along the [0001¯] crystallographic orientation (N-face). Plan-view high angle annular dark field (HAADF) STEM in the center of the micro-disks reveals a hexagonal lattice indicative of stacking faults. However, at the outskirt of the micro-disk, surprisingly, a honeycomb lattice is observed in plan view STEM indicating a perfect freestanding Wurtzite InN disk that is free of stacking faults. This result opens a pathway for realizing strain-free, freestanding InN substrates.

Growth of very large InN microcrystals by molecular beam epitaxy using epitaxial lateral overgrowth

Very thick InN (∼40 μm) was grown by molecular beam epitaxy using the epitaxial lateral overgrowth (ELO) technique. In some regions, the ELO of InN was observed as expected, indicating an important step toward fabricating quasi-bulk InN substrates. Interestingly, most parts of the sample consist of large flat-topped microcrystals and well-faceted microstructures. This is likely due to local growth condition variations during ELO, which is supported by an experiment where ELO of InN was performed on a substrate with various stripe mask patterns. TEM characterization of a flat top InN microcrystal revealed few stacking faults and only related threading dislocations. Defect-free small faceted microcrystals were also observed. The thick InN crystals show a narrow photoluminescence spectrum with a peak at 0.679 eV and linewidth of 16.8 meV at 4 K.

InN layers grown by the HVPE

AbstractWe report on the properties of high quality HVPE InN and on successful subsequent MBE growth of InN layers with improved characteristics on HVPE InN template substrates. InN layers were grown by HVPE on GaN/sapphire HVPE templates. The (00.2) XRD rocking curve of the best InN layer (RC) had the FWHM of about 375 arc sec, being the narrowest XRD RCs ever reported for HVPE InN. Transmission Electron Microscopy (TEM) revealed that at the GaN/InN interface, the threading dislocations that come from GaN were transmitted into the InN layer. We estimated the dislocation density in HVPE grown InN to be in the low 109 cm–2 range. Reflection high energy electron diffraction (RHEED) confirmed monocrystalline structure of the InN layers surface. Layers photoluminescence (PL) showed edge emission around 0.8 eV. Hall measured free electron concentration was in the range of 1019 ‐1020 cm–3 and electron mobility was ∼200 cm2/V s. MBE growth of InN was performed on the HVPE grown InN template substrate demonstrating the improvement of material quality in the case of homo‐epitaxial growth of InN. Demonstration of the high quality HVPE InN materials opens a new way for InN substrate development. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface strain and hexagonal/cubic polymorphism in InGaN epitaxy: first‐principles study

AbstractThe energetics and the growth dynamics of InGaN layers on strained InN substrates are studied using the first‐principles calculations. It is shown that the diffusion of adsorbed atoms on the surface is suppressed when the grown layers receive the tensile stress from the substrate.and the bonding between adsorbed and surface atoms is weakened. The present results indicate that the surface strain is one of relevant factors to promote InGaN hexagonal/cubic polymorphism in epitaxy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Static responses of a multilayered anisotropic piezoelectric structure to point force andpoint charge**Publication of the National Institute of Standards and Technology, an agency of the USGovt; not subject to copyright.

This paper studies three-dimensional (3D) static responses of a multilayered anisotropicpiezoelectric structure due to a point force and point charge. The materials in each layerare homogeneous, generally anisotropic, and linearly piezoelectric, and in general differentfrom one another. The interfaces between adjacent layers are perfectly bonded. Thegeneralized Stroh formalism and two-dimensional (2D) Fourier transforms areemployed to find the responses in terms of a 2D integral. For a layered structuremade of ten alternating layers of piezoelectric AlN and InN on an InN substrate,we show that the responses due to the point force and point charge are greatlyinfluenced by the material layering, showing complicated patterns through the layerthickness. Furthermore, the responses exhibit the asymptotic behavior in the case ofhomogeneous infinite space/half-space in a very short distance to the point source, aboutone tenth of the layer thickness. The complicated responses due to the layeredheterogeneity dictate the need for a general 3D analysis in the design of such smartstructures.

Thermodynamic study on compositional instability of InGaN/GaN and InGaN/InN during MBE

Thermodynamic analyses were carried out to understand influence of lattice constraint from GaN and InN substrates on relationship between solid composition x of In x Ga 1− x N films and input mole ratio R In (= P In 0/( P In 0+ P Ga 0) where P i 0 is the input partial pressure of element i) during molecular beam epitaxy. The calculated results suggest that compositional unstable region is found at small R In region for InGaN on InN while that for InGaN on GaN can be seen at large R In region at higher temperatures. This implies that InN-rich thin films are possible to form on InN substrate though it is difficult to form on GaN substrate.

Mote Carlo simulation of alloy phase diagrams of InGaN film pseudomorphic to GaN and InN substrates

Mote Carlo simulation of alloy phase diagrams of InGaN film pseudomorphic to GaN and InN substrates