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A thick AlN epilayer with an approximately 1.25-mm thickness was grown on a sapphire substrate by using a mixed source (Al+Ga of very small amount) at around 1150 °C for 2 hours and a mixed-source hydride vapor phase epitaxy (HVPE) method in a simplified reactor interlinked in series with no separation between the source and the growth zones. The simplified reactor was designed to minimize the reaction between quartz and AlCl vapor species of a high partial pressure at around 1150 °C. Thegrowthofthe thickAlN epilayerseemed to be due to theveryhighgrowthrate (maximum value of 600 µm/h) resulting from the minimization of the response distance between the vapor species and the source gases caused by interlinking in series the edge of the source zone with the substrate in the growth zone. The characteristics of the grown thick AlN epilayer were investigated by using cross-sectional scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Raman spectrometry and X-ray diffraction (XRD).

Four AlN nanowire-like structures were simultaneously grown directly without a buffer layer on four substrates-sapphire, quartz, Si(111), and 6H-SiC-via a mixed-source hydride vapor phase epitaxy (HVPE) method using a mixed source (Al+Ga) containing a small quantity of Ga at 1150 °C for 2 h. Deposition was carried out using a simplified reactor designed in series without any separation between the source and the growth zones. AlN nanostructures with hexagonal crystal structures were grown successfully and directly on thin, pre-grown AlN nucleation areas on the quartz substrates. Furthermore, AlN nanostructures were grown on the sapphire substrate without a buffer layer and on pre-grown epilayers on the Si (111) and the 6H-SiC substrates, respectively. The characteristics of the AlN nanowire-like structures grown on the four substrates were investigated using energy-dispersive X-ray spectrometry and field-emission scanning electron microscopy.

AIN epilayers of different thicknesses were grown directly on sapphire substrates without a buffer layer by using a mixed (Al+Ga) source containing 95 at% Al and a mixed-source hydride vapor phase epitaxy (HVPE) method at a temperature of around 1120°C. The grown epilayers consisted of an AlN alloy in the upper region and an AlGaN alloy in the nucleation region just above the sapphire substrate. The upper part of the epilayer gradually transformed from AlGaN into AlN owing to a decrease in the Ga content of the AlGaN alloy grown on the sapphire substrate with increasing growth thickness. The role of Ga in the mixed (Al+Ga) source in the growth of the epilayer directly on the sapphire substrate and the dependence of the growth mechanism of the epilayer with varying Ga contents on the growth thickness were investigated. We found that Ga in the mixed (Al+Ga) source only acted as an activation material that generated gaseous precursors rather than directly contributing to the growth of the epilayers. The mixed-source HVPE method appears suitable for the growth of thick AIN epilayers.

An electrode-evaporation technology on both the top and bottom sides of the bare vertical-type single chip separated from the traditional substrate by cooling, was developed for III-nitride vertical-type single chip LEDs with thick GaN epilayer. The post-process of the cooling step was followed by sorting the bare vertical-type single chip LEDs into the holes in a pocket-type shadow mask for deposition of the electrodes at the top and bottom sides of bare vertical-type single chip LEDs without the traditional substrate for electrode evaporation technology for vertical-type single chip LEDs. The variation in size of the hole between the designed shadow mask and the deposited electrodes owing to the use of the designed pocket-type shadow mask is investigated. Furthermore, the electrical and the optical properties of bare vertical-type single chip LEDs deposited with two different shapes of n-type electrodes using the pocket-type shadow mask are investigated to explore the possibility of the e-beam evaporation method.

Although hexagonal (2H) silicon (Si) semiconductors exhibit excellent optical properties owing to their quasi-direct bandgap, their growth conditions, which require extremely high pressures, preclude their widespread use in industrial applications. The current study, therefore, proposes a novel approach for the facile growth of hexagonal Si at atmospheric pressure via a unique phenomenon known as Al-based nano absorber. A mixed-source hydride vapor phase epitaxy (HVPE) method was used for the growth of the hexagonal Si single crystals employing a rapid interaction between GaCl3, AlCl, and SiClngases at a high temperature of 1200 °C using a source mixture of Ga, Al, and Si. In this process, the Al-based nano absorber was formed, which resulted in the absorbance of Si atoms, rather than the growth of Al-based nano absorber, to form the Si crystals due to the subsequent lack of GaCl3and AlCl sources. The hexagonal Si structure of these Si crystals was confirmed using field emission scanning electron microscopy, high-resolution x-ray diffraction spectroscopy, and Raman spectroscopy. Thus, the current study establishes atmospheric pressure mixed-source HVPE as a facile approach for growing various allotropic crystals such as Si, C, or Ge via absorption of other atoms by an Al-based nano absorber.

A carbon microsphere of a core-shell type was grown by using a new method of mixed-source hydride vapor phase epitaxy (HVPE). The surface and the cross section of the carbon microsphere grown by using the new method were observed by using scanning electron microscopy (SEM). The characteristics of the carbon microsphere were investigated by using X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM). From these measurements, the diameters of the carbon spheres were about a few hundred micrometers. Furthermore, we showed that carbon microspheres of the core-shell type could be grown successfully by using a mixed-source HVPE method and that they had larger sizes than those grown by using existing methods. This mixed-source HVPE method is proposed as a new method for making carbon microspheres.

A thick AlN epilayer is grown directly on a c-plane sapphire substrate by using the hydride vapor phase epitaxy (HVPE) method with a small quantity of Al. The new type (RF + hot-wall) flow HVPE reactor used in the AlN epilayer growth is custommade. The growth temperatures of the source and the growth zones are set at 950 °C and 1145 °C, respectively. The characteristics of the AlN layer grown on a sapphire substrate are investigated by using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The value of the full width at half maximum (FWHM) for the (002) peak from the AlN layer on the sapphire substrate is observed at 790 arcsec. From the small value of the FWHM, the AlN layer seems to be a well-arranged plane with a uniform (002) growth direction on a sapphire substrate.

The behavior of multiple quantum well GaAs/AlxGa1−xAs semiconductor superlattices with different dielectric interfaces are considered under magnetic and electric fields perpendicular and parallel to the superlattice axis, respectively. The parabolic confining potential well was varied with the compositional rate of the AlxGa1−xAs barrier. Taking into account intrasubband and intersubband transitions and using random phase approximation, the density-density correlation function is calculated as a function of the magnetic field strength, compositional rate, and averaged electric field strength over the quantum well. In this way, the dispersion of the surface and bulk state energies are obtained. The Raman intensities for these states are also obtained as a function of incoming light energy for various averaged electric field strengths over the quantum well.

Extending our previous theoretical framework, we study the heat capacity of a canonical ensemble, including the Zeeman effect, under an incident magnetic field at a specific angle with respect to the axis of the quantum-dot superlattices (QDSL’s) and confined by an isotropic parabolic potential for GaAs, InAs, and InSb, respectively. Furthermore, we numerically obtain the dependences of the heat capacity on the angle between the incident magnetic field’s direction and the superlattice axis for an isotropic, confining, parabolic potential as functions of the temperature, the effective g-factor value, and the confinement frequency in the QDSL’s of GaAs, InSb, and InAs, respectively. Particularly, the dependence of the heat capacity on the angle of the incident magnetic field is discussed in detail.

The GaN layer was typical III-V nitride semiconductor and was grown on the sapphire substrate which cheap and convenient. However, sapphire substrate is non-conductivity, low thermal conductivity and has large lattice mismatch with the GaN layer. In this paper, the poly GaN epilayer was grown by HVPE on the metallic compound graphite substrate with good heat dissipation, high thermal and electrical conductivity. We tried to observe the growth mechanism of the GaN epilayer grown on the amorphous metallic compound graphite substrate. The HCl and gas were flowed to grow the GaN epilayer. The temperature of source zone and growth zone in the HVPE system was set at and , respectively. The GaN epilayer grown on the metallic compound graphite substrate was observed by SEM, EDS, XRD measurement.

A finite type-I superlattice with different dielectric media on either side of the surfaces is considered under a perturbing electric fields parallel to the superlattice axis on the basis of an infinite square potential well. Using the random-phase approximation, the density–density correlation function including intra- and inter-level transitions in a multiple-quantum-well (MQW) is calculated. The dispersion relations for the surface and the bulk states are obtained as functions of the momentum wave vector and the averaged electric field strength over the quantum well. The Raman intensities due to the bulk and the surface plasmons for the intra- and the inter-level transitions are also obtained for incoming light energy.

We investigate the heat capacity using the previous theoretical framework for the electronic system in the quantum-dot superlattices (QDSL’s), including the Zeeman effect of GaAs, InAs, and InSb, respectively, by using an isotropic parabolic potential under a magnetic field on the basis of canonical ensemble statistics. We numerically study the dependences of the heat capacity on the confinement frequency of the isotropic parabolic potential and the electronic density as functions of the temperature and the magnetic field strength in the QDSL’s of GaAs, InSb, and InAs, respectively. Furthermore, we numerically obtain the dependences of the heat capacity on the effective g-factor value in the QDSL’s of GaAs, InSb, and InAs, respectively, as functions of the temperature and the magnetic field strength.

The AlGaN layer has direct wide bandgaps ranging from 3.4 to 6.2 eV. Nowadays, it is becoming more important to fabricate optical devices in an UV region for the many applications. The high quality AlGaN layer is necessary to establish the UV optical devices. However, the growth of AlGaN layer on GaN layer is difficult due to the lattice mismatch and difference thermal expansion coefficient between GaN layer and AlGaN layer. In this paper, we attempted to grow the LED structure on GaN template by mixed-source HVPE method with multi-sliding boat system. We tried to find the optical and lattice transition of active layer by control the Al content in mixed-source. For the growth of epi layer, the HCl and gas were flowed over the mixed-source and the carrier gas was . The temperature of source zone and growth zone was stabled at 900 and , respectively. After the growth, we performed the x-ray diffraction (XRD) and electro luminescence (EL) measurement.

(Received October 12, 2011)(Revised October 24, 2011)(Accepted November 11, 2011)Abstract In general, the fabrications of the LEDs with mesa structure are performed grown by MOCVD method. In orderto etch and separate each chips, the LEDs are passed the RIE and scribing processes. The RIE process using plasma dryetching occur some problems such as defects, dislocations and the formation of dangling bond in surface result in declineof device characteristic. The SAG method has attracted considerable interest for the growth of high quality GaN epi layeron the sapphire substrate. In this paper, the SAG method was introduced for simplification and fabrication of the highquality epi layer. And we report that the size of selective area do not affect the characteristics of original LED. Thediameter of SAG circle patterns were choose as 2500, 1000, 350, and 200µm. The SAG-LEDs were measured to obtainthe device characteristics using by SEM, EL and I-V. The main emission peaks of 2500, 1000, 350, and 200µm were 485,480, 450, and 445 nm respectively. The chips of 350, 200µm diameter were observed non-uniform surface and resistancewas higher than original LED, however, the chips of 2500, 1000µm diameter had uniform surface and current-voltagecharacteristics were better than small sizes. Therefore, we suggest that the suitable diameter which do not affect thecharacteristic of original LED is more than 1000µm.Key wordsSelective area growth, InGaN/GaN, Multi quantum well, MOCVD, Band-filling effect, Screening effect

The angular dependence of the optically detected magnetophonon resonance (ODMPR) for the frequency-dependent magnetoconductivity in a Ge-based (nonpolar) semiconductor superlattice under a tilted magnetic field is investigated. The frequency-dependent magnetoconductivity, including the miniband width, the periodic potential, the photon frequency, and the tilt angle of a magnetic field tilted relative to the superlattice axis, is calculated using the nonpolar LO phonon modes as a function of the magnetic field strengths. In particular, the angular dependence of the ODMPR lineshape, such as the splitting and the shift of the ODMPR peaks for the photon frequency, is discussed. Furthermore, the angular dependences for the appearance of the plateau region between two neighboring ODMPR peaks and the change in the ODMPR amplitude as a function of the tilt angle of the tilted magnetic field for various miniband widths and photon frequencies are discussed in detail.

In this paper, we report structural changes in InGaN micro-structures grown by using mixed-source hydride vapor phase epitaxy (HVPE). Hexagonal nanorods, bunched with many submicron-sized legs and tetrapod-shaped InGaN micro-structures, are grown on r-plane sapphire, c-plane sapphire and Si (111) substrates. As the growth temperature is increased, the overall shape of the InGaN structures changes from clusters of some needle-like legs to bunch shapes of many legs with thicker and hexagonal edges. The grown InGaN structures were analyzed by using X-ray photoelectron spectroscopy (XPS) to characterize the InGaN ternary crystal alloy. The indium mole fractions of the InGaN structures grown at 650 C, 700 C and 750 C were 44 %, 37 % and 27 %, respectively.

The selective area growth (SAG) of AlGaN/InGaN/AlGaN light-emitting diodes (LEDs) is performed by mixed-source hydride vapor phase epitaxy (HVPE). The structure is grown on a n-GaN templated (0001) sapphire substrate. The SAG-double heterostructure (DH) is consisted of a Te-doped AlGaN cladding layer, an InGaN active layer, a Mg-doped AlGaN cladding layer, and a Mg-doped GaN capping layer. All of the epitaxial layers of LED structure are grown consecutively with a multi-sliding boat system. Room-temperature electroluminescence (EL) characteristics show an emission peak wavelength of 400 nm with a full width at half-maximum (FWHM) of approximately 0.38 eV (at 20 mA). We find that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of III-nitride LEDs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The selective area growth (SAG) of AlGaN/InGaN/AlGaN light-emitting diodes (LEDs) is performed by mixed-source hydride vapor phase epitaxy (HVPE). In order to obtain the SAG-AlGaN/InGaN/AlGaN heterostructure, a special graphite fixture to use in HVPE is designed. First, an n-type AlGaN layer is grown at 1090 °C on a GaN templated (0001) sapphire substrate with a patterned SAG-structure of a silicon oxide (SiO2). On this selectively grown n-type AlGaN layer, a nominally undoped-InGaN layer is grown using an In-Ga mixed metallic source at 990 °C. After the growth of InGaN layer, Mg-doped AlGaN and Mg-doped GaN layers are grown as a cladding and capping layers at 1090 °C and 1050 °C, respectively. All of the epitaxial layers of LED structure are grown consecutively with a multi-sliding boat system. Room-temperature electroluminescence (EL) characteristics show an emission peak wavelength of 415 nm with a full width at half-maximum (FWHM) of approximately 0.37 eV. We find that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of III-nitride LEDs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The InGaN layers on GaN templated sapphire (0001) and Si (111) substrates are grown by mixed-source hydride vapor phase epitaxy (HVPE) method. As a new attempt in obtaining an InGaN layers, the growth of the thick InGaN layer is performed by putting small amount of Ga into the In source. The InGaN layer is compounded from chemical reaction between a NH3 and an Indium-gallium chloride formed by HCl flown over metallic In mixed with Ga. The InGaN layer is analyzed by X-ray photoelectron spectroscopy (XPS) to characterize the InGaN ternary crystal alloy. The optical property of the selective area growth (SAG) of the InGaN layer is investigated by the photoluminescence (PL) spectrum and the cathodoluminescence (CL) images. Indium compositions are estimated to be in the range 3-10%. In order to obtain the GaN layer on GaN templated Si (111) substrates, an InGaN layer is used as an intermediate layer. The PL and CL of the InGaN intermediate layer are measured at 300K. We find that the InGaN intermediate layer is possible to be one of the growth methods of thick GaN layer on Si substrates by HVPE method. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We obtain the angular dependence of magnetophonon resonance (MPR) peaks from longitudinal magnetoconductivities of GaAs/AlAs semiconductor superlattices for longitudinal optical (LO) phonons in tilted magnetic field applied to the superlattice axis. The MPR peaks of both GaAs and AlAs LO phonon modes using the second derivative of the magnetoconductivities including a miniband width and a periodicity of the potential are shown. As the tilt angle of the applied magnetic fields is increased, the MPR peak positions are shifting to higher magnetic strength region whereas the peak amplitudes are decreasing to vanish at the same condition with experiments. Our results are in qualitative good agreement with the experimental results. We also get the resonance fields for the MPR peak numbers of the GaAs and AlAs LO phonon modes as a function of the tilt angles. Furthermore, we obtain the dispersion relations and the density of states (DOS) including a miniband width, a periodicity of the potential and tilt angles of the tilted magnetic fields to explain the appearance of plateau region between neighboring peak amplitudes. The plateau region can be explained by phenomena such as the shifts, the decreases, and the disappearances of the peak amplitudes of the magnetoconductivities and the second derivative of magnetoconductivities of GaAs/AlAs semiconductor superlattices for tilt angles of the applied magnetic fields.

The AlxGa1–xN, Te-doped GaN and Mg-doped GaN layers on GaN/Al2O3 substrates are grown by mixed-source hydride vapor phase epitaxy (HVPE) method. The metallic Ga mixed with Al is used as group III source material to get the AlxGa1–xN layers. The values of the compositions x of the AlxGa1–xN layers characterized by X-ray diffraction (XRD) measurements are 0.6% ∼ 80% at the various temperatures of the source zone. The metallic Ga mixed with Te (or Mg) is used as source material for n-type (or p-type) doping. The electron concentrations of the Te-doped GaN layers are varied from 1.8 × 1017 to 8.3 × 1018/cm3. The hole concentrations of the Mg-doped GaN layers are varied from 1.5 × 1016 to 3.2 × 1016/cm3. We find that the mixed-source HVPE method is suitable to get a thick AlGaN layer with an arbitrary composition, a Te-doped GaN layer with a high n-type concentration and a Mg-doped GaN layer with p-type concentration. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The AlxGa1–xN layers on GaN/Al2O3 substrates are grown by mixed-source hydride vapor phase epitaxy (HVPE) at various temperatures of the source zone. We find source zone temperature dependence of the composition x of AlxGa1–xN layers. Te doping as a new attempt and Si doping in obtaining an n-type AlGaN layers are performed by putting small amount of Te (or Si) into the Ga-Al source, respectively. In case of Te-doped AlGaN (x = 0.16), the carrier concentration is varied from 1.1 x 1018 to 8.0 x 1018/cm3, while in case of Si-doped one, it is varied from 2.0 x 1016 to 1.1 x 1017/cm3. We find the new results that Te doping is more suitable to get a high n-type concentration by mixed-source HVPE. InGaN/GaN multiple quantum wells (MQWs) are grown on the selective area growth (SAG)-Te-doped AlGaN and SAG-Si-doped AlGaN cladding layer by mealorganic chemical vapour deposition (MOCVD), respectively. Furthermore, we investigate the electroluminescence (EL) properties of SAG-LEDs of two different cladding layers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical detected electrophonon resonance (ODEPR) effects in quantum wells of n-GaAs materials are investigated for square potential and parabolic potential, respectively. We also obtain the ODEPR conditions as functions of confinement frequency in parabolic potential and well-width in square potential for the various photon frequencies, respectively. In particular, anomalous behaviors of the ODEPR lineshape such as the splitting of ODEPR peaks for incident photon frequency are discussed. Furthermore, we obtain the selection rules for transition in quantum wells of two different potentials, respectively.

Using mixed-source hydride vapor-phase epitaxy (HVPE), an AlGaN layer with high Al content on GaN/Al2O3 substrate is obtained. The AlGaN layer grown by mixed-source HVPE is characterized by X-ray diffraction (XRD) measurements and cathodoluminescence (CL) spectra. In the mixed-source HVPE technique, the AlGaN material is compounded from the chemical reaction between NH3 and an aluminum–gallium chloride formed using HCl that is flowed over metallic Ga mixed with Al. The XRD measurements indicate that single-crystal hexagonal AlGaN with high Al content had been grown. The CL spectra at 4 K show that the distribution of the Al on the AlGaN surface for very high Al content (x = 0.8 in AlxGa1–xN) is not uniform. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth of a thick AlGaN layer on GaN/Al2O3 substrate is performed by mixed-source hydride vapor phase epitaxy (HVPE) method. The AlGaN material is compounded from chemical reaction between a NH3 and an aluminum-gallium chloride formed by HCl which is flown over metallic Ga mixed with Al. The AlGaN epitaxial layer is analyzed by Auger-electron spectroscopy (AES) and X-ray diffraction (XRD) measurement to characterize the AlGaN. Al concentration is estimated to be in the range of 0.5–6%. We suggest that the metallic Ga mixed with Al can be used as a group III source material in the HVPE growth of the AlGaN layer.

Using the random-phase approximation, the density–density correlation function including intra- and inter-Landau level transitions in multiple quantum wells is obtained under magnetic fields parallel to interfaces, on the basis of a simple model of parabolic confining potentials. The Raman intensities for the bulk and surface magnetoplasmons are investigated as a function of the number of quantum wells, the ratio of the confining potential parameter to cyclotron resonance frequency, and the momentum wave vector.

We prepared InGaN light-emitting diodes (LEDs) with the active layers grown from a mixed source of Ga–In–N materials on an n-type GaN substrate by a selective-area growth method and three fabrication steps: photolithography, epitaxial layer growth, and metallization. The preparation followed a previously developed experimental process using apparatus for mixed-source hydride vapor-phase epitaxy (HVPE), which consisted of a multi-graphite boat, for insulating against the high temperature and to control the growth rate of epilayers, filled with the mixed source on the inside and a radio-frequency (RF) heating coil for heating to a high temperature (T > 900 °C) and for easy control of temperature outside the source zone. Two types of LEDs were prepared, with In compositions of 11.0 and 6.0% in the InGaN active layer, and room-temperature electroluminescence measurements exhibited a main peak corresponding to the In composition at either 420 or 390 nm. The consecutive growth of InGaN LEDs by the mixed-source HVPE method provides a technique for the production of LEDs with a wide range of In compositions in the active layer.