Morphology and surface electronic structure of MBE grown InN (original) (raw)
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Indium Nitride (InN) Nanostructures Grown by Plasma-Assisted Molecular Beam Epitaxy (PAMBE)
Indium nitride (InN) is an interesting and potentially important semiconductor material with superior electronic transport properties. Compared to all other group III-nitrides, InN possesses the lowest effective mass, the highest mobility, the highest saturation velocity and narrow band gap of 0.7-0.9 eV. The present paper deals with the fabrication of InN nanostructures on silicon and sapphire substrates by plasma-assisted molecular beam epitaxy. The droplet epitaxy and Stranski-Krastanov(S-K) growth modes were used to grow the nanostructures.
physica status solidi (b), 2006
Unintentionally doped InN has been grown onto an atomically flat AlN intermediate layer on top of the Si(111) substrate using plasma-assisted molecular beam epitaxy (PA-MBE). Though there are lots of micrometer-size indium droplets randomly distributed on the top of the surface, the highest electron mobility of this InN thin film measured at room temperature by van der Pauw method is still higher than 1000 cm 2 /V s with a carrier concentration of 5 -8.9 × 10 18 cm -3 . A symmetrical X-ray rocking curve is measured and the full-width-at-half-maximum (FWHM) of this sample is 1089 arcsec. In the meantime, the threading dislocation (TD) density of this material is estimated to around 9.8 × 10 8 cm -2 -7.5 × 10 9 cm -2 depending on the probing regions that are studied by the etching technique and field-emission scanning electron microscopy (FE-SEM). (2 × 1) in situ reflection high-energy electron diffraction (RHEED) patterns show that this sample is grown under In-rich environment with possible In-terminated surface. From the FE-SEM pictures which were taken from the samples after 10 minutes etching in hydrochloride, the surface morphology shows In-polarity-like patterns that coincide with those procured in RHEED. To select and grow a high-quality laminated AlN as intermediate layer is believed to be the major step in obtaining this high electron mobility InN thin film on Si substrate.
Acta Materialia, 2007
Raman scattering has been used to study lattice defects induced by non-stoichiometry in indium nitride films grown by plasmaassisted molecular beam epitaxy with different In/N ratios. A gap mode located at about 375 cm À1 is observed in InN films grown at low In/N ratios. This is in good agreement with the recursion method calculation for the In vacancy-induced vibration mode. In addition, a spatial correlation model has been used to estimate the lattice disorder in InN samples. The shortest correlation length is L = 5.9 nm.
Applied Physics Letters, 2006
The structure and surface bonding configuration of InN layers grown by high-pressure chemical vapor deposition have been studied. Atomic hydrogen cleaning produced a contamination free surface. Low-energy electron diffraction yielded a 1 ϫ 1 hexagonal pattern demonstrating a well-ordered c-plane surface. High-resolution electron energy loss spectra exhibited a Fuchs-Kliewer surface phonon and modes assigned to a surface N-H species. Assignments were confirmed by observation of isotopic shifts following atomic deuterium cleaning. No In-H species were observed, and since an N-H termination of the surface was observed, N-polarity indium nitride is indicated.
Journal of Crystal Growth, 2009
This article investigates the growth of InN layers on (1 0 0) InP in ultra-high vacuum using a glow discharge source (GDS). Auger electron spectroscopy (AES) was used to understand the different steps of the nitridation process with the analysis of In-MNN, N-KLL and P-LMM transitions. A modeling of Auger signals using a stacked layers model allows us to confirm that four monolayers of indium nitride are created on (1 0 0) InP. InN layers grown on (1 0 0) InP were studied optically by photoluminescence (PL) spectroscopy versus the excitation power and the sample temperature (10-300 K). Results show broad spectral band energy close to the lowest reported InN bandgap. The temperature dependence of the PL peak energy showed a S-shaped behavior (decrease-increasedecrease). The results suggest that the InN-related emission is significantly affected by the change in carrier dynamics with increasing temperature: the effect can be due to the large exciton localization effects.
Growth of InN films by RF plasma-assisted MBE and cluster beam epitaxy
Journal of Crystal Growth, 2006
This paper describes the growth, structure, transport and optical properties of InN films grown by MBE using either nitrogen radicals (N 2 * ) produced by a RF plasma source or clusters containing on the average 2000 nitrogen molecules (N 2 ) 2000 . The InN films were grown at temperatures between 300 and 600 1C on (0 0 0 1) sapphire substrates using either an InN buffer or a GaN template. It was found that the conversion of the surface of the sapphire from Al 2 O 3 to AlN, by exposing it to active nitrogen, is essential for the growth of singlecrystalline InN films. Thick films (2-3 mm), produced by the plasma source, tend to delaminate from the substrate presumably due to extreme compressive stresses. On the other hand, films adhere better if nitridation of the sapphire substrate and the low-temperature InN buffer are grown by the cluster source. All films are auto-doped n-type with carrier concentration higher than 3 Â 10 18 cm À3 and best room temperature mobility 1130 cm 2 /V s. The energy gap of InN was determined to be 0.77 eV. The plasma frequency was measured by infrared reflectivity and the data were used to determine the electron effective mass (0.09m 0 ). We found that the measured optical gap and the electron effective mass are in qualitative agreement with the predictions of the k Á p method for direct semiconductors. r
2007
Electronic and structural properties of InN layer grown by high pressure chemical vapor deposition have been studied by high-resolution electron energy loss spectroscopy ͑HREELS͒ and room temperature infrared reflection measurements. HREEL spectra after atomic hydrogen cleaning exhibit N-H bending and stretching vibrations with no indications of an indium overlayer or droplet formation. Broad conduction band plasmon excitations are observed centered at 3100-4200 cm −1 at various locations across the surface in HREEL spectra acquired with 25 eV incident electron energy. The plasmon excitations are shifted about 300 cm −1 higher in spectra acquired using 7 eV electrons due to higher plasma frequency and carrier concentration at the surface than in the bulk which indicates surface electron accumulation. Infrared reflectance data acquired at various spots across the surface showed a similar variation in bulk plasma frequency. A three phase thin film reflection model fitted to the infrared data yielded carrier concentrations from 8.2ϫ 10 19 to 1.5ϫ 10 20 cm −3 and carrier mobilities from 105 to 210 cm 2 /V s.
Surface Science, 2007
Surface termination and electronic properties of InN layers grown by high pressure chemical vapor deposition have been studied by high resolution electron energy loss spectroscopy (HREELS). HREEL spectra from InN after atomic hydrogen cleaning show N-H termination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad conduction band plasmon excitations are observed centered at 3400 cm À1 in HREEL spectra with 7 eV incident electron energy which shift to 3100 cm À1 when the incident electron energies are 25 eV or greater. The shift of the plasmon excitations to lower energy when electrons with larger penetration depths are used is due to a higher charge density on the surface compared with the bulk, that is, a surface electron accumulation. These results indicate that surface electron accumulation on InN does not require excess indium or In-In bonds.