Shugo Nitta

STRUCTURAL PROPERTIES OF INN ON GAN GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

InN has been expected to be a suitable material for electronic devices such as high mobility transistors because of its small effective mass compared to other nitrides. Heteroepitaxial InN films were grown by metalorganic vapor-phase epitaxy. The films have been structurally characterized by triple-axis x-ray diffraction (XRD) analysis in terms of lattice-mismatch dependence and InN film thickness dependence, and Hall measurements have been performed. In the XRD measurement, ω and ω–2θ scans were used, and the degree of tilting (the linewidth of x-ray signal, Δωc) [(0002) reflection] and that of twisting (Δωa) [(1010) reflection] have been separated. In addition, the degree of distribution of lattice constant c (Δ2θc) [(0002) reflection] of InN films has been assessed. For study of the lattice-mismatch dependence, growth of InN films on GaN, AlN and directly on sapphire substrates was performed, and accordingly, Δωc was found to range from about 500 to 4000 arcsec, and Δ2θc from about 400 to 700 arcsec. ...

Anomalous features in the optical properties of Al1−xInxN on GaN grown by metal organic vapor phase epitaxy

We have studied the optical properties of Al1−xInxN thin films grown on GaN by metal organic vapor phase epitaxy. X-ray diffraction analysis of ω and ω-2θ scans showed that both the compositional fluctuation and the degree of crystalline mosaicity increase with increasing x. While the energy positions of both the absorption edge and photoluminescence peak shift to a lower-energy region with increasing x, the linewidth of the photoluminescence spectra and the value of the absorption edge tail decrease. The Stokes shift also decreases with increasing x, following which both energy positions become 1.66 eV, which is smaller than the band gap of InN (1.9 eV). These anomalous features of the optical properties of Al1−xInxN might be affected by the absorption in the infrared region caused by the high electron concentration.

Structural and optical properties of AlInN and AlGaInN on GaN grown by metalorganic vapor phase epitaxy

We studied structural and optical properties of Al 1~x In x N and Al 1~y~z Ga z In y N films. The films were grown on GaN by atmospheric pressure metalorganic vapor-phase epitaxy. GaN was grown on a c-plane sapphire substrate with a low-temperature-deposited AlN bu⁄er layer. Photoluminescence (PL), absorption and X-ray di⁄raction measurements of Al 1~x In x N showed that PL and absorption spectral peaks shift to lower photon energy with increasing alloy composition x and that Al 0.83 In 0.17 N has the highest crystallinity. ( 1998 Elsevier Science B.V. All rights reserved.

Control of Dislocations and Stress in AlGaN on Sapphire Using a Low Temperature Interlayer

In organometallic vapor phase epitaxial growth of AlGaN on sapphire, the role of the low-temperature-deposited interlayers on a high-temperature-grown GaN layer was investigated by in-situ stress measurement, X-ray diffraction, and transmission electron microscopy. Crack-free and low-dislocation-density AlGaN with the whole compositional range has been realized on the sapphire substrate.

Metalorganic vapor phase epitaxy growth of crack-free AlN on GaN and its application to high-mobility AlN/GaN superlattices

We have succeeded in growing crack-free AlN of even 0.5 μm thickness on GaN by metalorganic vapor phase epitaxy. A (0001) sapphire substrate was used. Crack-free AlN was grown on GaN at 1000 °C with N2 carrier gas. An AlN layer was grown on GaN of 2 μm thickness grown at 1050 °C, following the low-temperature deposition of an AlN buffer layer of 30 nm. No cracks were observed in the microphotographs of AlN on GaN grown using N2. X-ray diffraction analysis revealed that AlN/GaN superlattices (SLs) were coherently grown on GaN, and satellite peaks up to the third order were observed. The structure of AlN/GaN SLs on GaN showed a maximum electron mobility of 1580 cm2/V s at room temperature and a nominal sheet carrier density of 8.4×1012 cm−2.

Strain relief and its effect on the properties of GaN using isoelectronic In doping grown by metalorganic vapor phase epitaxy

We studied the effect of isoelectronic In doping on the crystalline and optical properties of GaN grown on sapphire with H2 or N2 carrier gas by metalorganic vapor phase epitaxy. The relationship between lattice constants c and a obtained by x-ray diffraction analysis showed that with increasing trimethylindium (TMI) flow during growth, the strain in GaN decreased, and accordingly, the tilting and the twisting components of crystalline mosaicity also decreased. In addition, the Raman shift, the excitonic photoluminescence peak energy, and the its linewidth shifted in accordance with the magnitude and the sign of the strain in GaN, regardless of the carrier gas used. These results revealed that for a smaller TMI flow region, In was incorporated so that the crystallinity of GaN improved, and for a larger TMI flow region, In substituted for Ga so that alloying formation might have occurred.

Mass transport and the reduction of threading dislocation in GaN

This is the first report of the observation of mass transport of single crystalline GaN. A wafer with the squared grooves was annealed at 1100°C under flows of NH3 and N2. During the annealing, no group-III alkyl source gas was supplied. After 12 min annealing, all the stripes were buried due to a mass transport of GaN from the unetched region. The mechanism of mass transport is discussed. The strong crystallographic anisotropy of GaN is expected to modulate the shape of the mass transported region. Transmission electron microscopy revealed that threading dislocations were bent and did not climb through the mass transported region. Therefore, a dislocation-free region was achieved at the upper part of the mass transported region except for one dislocation observed at the center of the groove. This method is promising for the fabrication of dislocation-free GaN on sapphire substrate.

Structural Properties of Al 1- xIn xN Ternary Alloys on GaN Grown by Metalorganic Vapor Phase Epitaxy

Michihiko KARIYA, Shugo NITTA, Shigeo YAMAGUCHI, Hisaki KATO, Tetsuya TAKEUCHI,Christian WETZEL, Hiroshi AMANO andIsamu AKASAKIDepartment ofElectrical and Electronic Engineering, Meijo University, 1-501Sl1iogamagucl1i, Tempaku-ku.Nagoya 468-8502.Japan(Received April 23, 1998; accepted for publication May 7,1998)Ah_xlnxN layers grown on GaN by metalorganic vapor phase epitaxy (MOVPE) have been structurally studied usingwand

m-Plane GaInN Light Emitting Diodes Grown on Patterned a-Plane Sapphire Substrates

The fabrication of a blue m-plane GaInN light emitting diode (LED) grown on an m-plane GaN layer grown on a 3-in. patterned sapphire substrate is reported. The output power of the LED was approximately 3 mW at the wavelength of 461 nm, a driving current of 20 mA, and a forward voltage of 3.5 V. This is the first report of nonpolar or semipolar blue LEDs grown on hetero-substrates with milliwatt scale output power.

m-Plane GaN Films Grown on Patterned a-Plane Sapphire Substrates with 3-inch Diameter

Nonpolar m-plane GaN films have been grown by metalorganic vapor-phase epitaxy on patterned a-plane sapphire substrates (diameter: 3 in.) without dielectric masks made of materials such as SiO2. The m-plane GaN layer had a smooth and transparent surface over the entire area of the substrate. Furthermore, the epitaxial relationships between the m-plane GaN film and the patterned a-plane sapphire substrate were as follows: [0001]GaN∥[0001]Sapphire and [1120]GaN∥[1010]Sapphire. The full width at half maximum values of the X-ray rocking curves for (1010) GaN along [1120]GaN and [0001]GaN were found to be 396 and 565 arcsec, respectively.