bluuebunny/crossref_metadata_2025_split huggingface dataset:
Platelets and needles: two habits of pressure grown GaN crystals
Authors: Bockowski M. , Grzegory I. , Łucznik B. , Kamler G. , Krukowski S. , Wróblewski M. , Kwiatkowski P. , Jasik K. , Porowski S. 
Published: June 2007

AbstractThe growth of the GaN needles by high pressure solution method is shown in details and compared to the platelets crystallization. The growth mechanism and main factors determining the crystal habit (needle and platelet) in high pressure solution method are presented and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inhomogeneity of InGaN quantum wells in GaN‐based blue laser diodes
Authors: Lee Sung‐Nam , Ryu H. Y. , Paek H. S. , Son J. K. , Sakong T. , Jang T. , Sung Y. J. , Kim K. S. , Ha K. H. , Nam O. H. , Park Y. 
Published: June 2007

AbstractWe investigated the inhomogeniety of InGaN quantum wells (QWs) with high In content in the GaN‐based blue laser diodes (LDs). The 2QWs LD structure show the twice higher photoluminescence intensity and the slightly higher electroluminescence intensity than single quantum well (SQW) LD. However, we can obtain the high power blue InGaN SQW LDs with the low threshold current density of 2.19 kA/cm2 and the high sloped efficiency of 0.8 W/A at the cw condition by reducing the number of QWs. From carrier distribution by simulation, blue InGaN 2QWs LDs represented the non‐uniformed hole distribution of n‐side 1st and p‐side 2nd well in InGaN/InGaN 2QWs region due to the low hole concentration and mobility of p‐type nitrides. From time‐resolved photoluminescence (TRPL), we obtained that 2QWs LD shows the some spatial localization states due to the multiple component PL decay process. Therefore, we can guess that the inhomogeniety of InGaN QWs would be quite restricted in deep InGaN QWs of GaN based blue LDs which results in significantly in homogeneities of QWs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evidence of quantum dot‐like nano‐objects in InGaN quantum wells provided by narrow photoluminescence spectra from localized exciton
Authors: Gotoh H. , Akasaka T. , Tawara T. , Kobayashi Y. , Makimoto T. , Nakano H. 
Published: June 2007

AbstractWe report on narrow photoluminescence (PL) spectra obtained from spatially localized excitons in InGaN quantum wells (QW). These PL lines (less than 1 meV wide) are clearly detected in QWs on several buffer structures and substrates with the micro‐PL technique in low temperature regions. A narrow PL spectrum is one of the characteristics of an exciton confined in a quantum dot (QD). Our results directly confirm that QD‐like nano‐objects exist in InGaN QWs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN deep ultraviolet LEDs on bulk AlN substrates
Authors: Ren Zaiyuan , Sun Q. , Kwon S.‐Y. , Han J. , Davitt K. , Song Y. K. , Nurmikko A. V. , Liu W. , Smart J. , Schowalter L. 
Published: June 2007

AbstractWe report the growth of sub‐300 nm ultraviolet light emitting diodes (UV LEDs) on bulk AlN substrates. Heteroepitaxial evolution study through interrupted growth experiments revealed that AlxGa1‐xN (x > 0.5) epilayers can be grown pseudomorphically with well‐defined step‐flow growth mode below a certain critical thickness. The build‐up of compressive strain energy eventually induces a morphological roughening followed by the admission of misfit dislocations. LEDs grown on bulk AlN substrates exhibit noticable improvement over those on sapphire in device impedance, efficiency and thermal characteristics under high‐level injection, pointing to a promising substrate platform for high performance III‐nitride ultraviolet optoelectronics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Implantation damage recovery and carrier activation studies of Si‐implanted Al0.18Ga0.82N by temperature dependent Hall‐effect measurements
Authors: Ryu Mee‐Yi , Yeo Y. K. , Hengehold Robert L. 
Published: June 2007

AbstractN‐type activation studies of Si‐implanted Al0.18Ga0.82N have been made as a function of anneal temperature and ion dose to obtain maximum possible activation efficiency. Nearly 100 and 95% electrical activation efficiencies were obtained for Si‐implanted Al0.18Ga0.82N with doses of 5x1014 and 1x1015 cm–2 and annealing at 1250 and 1200 oC for 25 min, respectively. The room temperature sheet resistivity decreases from 528 to 196 Ω/square with increasing anneal temperature from 1150 to 1250 oC for a dose of 5x1014 cm–2. Both sheet carrier concentration (activation efficiency) and mobility increase with anneal temperature, indicating an improved implantation damage recovery with anneal temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new system for growing thick InN layers by hydride vapor phase epitaxy
Authors: Kikuchi J. , Nishizawa Y. , Murakami H. , Kumagai Y. , Koukitu A. 
Published: June 2007

AbstractA new system for hydride vapor phase epitaxy (HVPE) of thick InN layers using Cl2 was investigated. Thermodynamic analysis was performed for the reactions at the source and the growth zones. It was found that InCl3 can be generated preferentially at the second source zone by adding Cl2 to InCl from the first source zone. The analysis for the growth zone showed that a significantly large driving force for InN deposition is expected. It was shown that the growth of thick InN layers is possible by employing the new HVPE system. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo study of high‐field electron transport characteristics in AlGaN/GaN heterostructure considering dislocation scattering
Authors: Tomita Yoshihiro , Ikegami Hirofumi , Fujishiro Hiroki I. 
Published: June 2007

AbstractThe effect of the threading dislocation on the high‐field electron transport characteristics in the AlGaN/GaN heterostructure is studied using the Monte Carlo (MC) simulation technique. The three‐dimensional (3D) relaxation time of the dislocation scattering, where the threading dislocation is modeled as a line of charge, is applied to the simulation. Our study shows that the threading dislocation has a small effect on the electron velocity in the AlGaN/GaN heterostructure as compared with that in the bulk n‐GaN, which is owing to the strong screening effect by the highly concentrated carriers in the two‐dimensional electron gas (2DEG). Consequently, the AlGaN/GaN‐HEMT is insensitive to the existence of the threading dislocation piercing through the channel. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lateral diffusion of photogenerated carriers in InGaN/GaN heterostructures observed by PL measurements
Authors: Vierheilig C. , Braun H. , Schwarz U. T. , Wegscheider W. , Baur E. , Strauß U. , Härle V. 
Published: June 2007

AbstractIn this paper we present a direct observation of the lateral diffusion of photogenerated carriers in InGaN/GaN quantum wells. The spatial distribution of the photoluminescence around a small exciting laser spot is analyzed by scanning in the focal plane of our confocal microscope. The results of a blue and a green emitting sample at varying excitation densities are discussed in the context of the theoretical model of the enhanced lateral diffusion. A lateral electric field which causes an additional radial drift motion was determined by analyzing the PL spectra and by solving a drift–diffusion equation for the lateral motion in the quantum well.
Growth and field emission of GaN nanowires grown by metal organic chemical vapour deposition
Authors: Inoue Y. , Tajima A. , Takeda S. , Ishida A. , Mimura H. , Sakakibara S. 
Published: June 2007

AbstractGallium nitride nanowires were grown on Si by Ni‐catalyst‐assisted metalorganic chemical vapor deposition via a vapor‐liquid‐solid growth mechanism. The GaN nanowires have a very high growth rate of >100 μm/h and a very high aspect ratio of 1000; ∼20 nm in diameter and ∼20 μm in length. In the field emission measurement, the GaN nanowires showed a low turn‐on field of 6 V/μm. The good result is attributed to the near‐vertical growth and the very high aspect ratio, as well as a low electron affinity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Si+ implanted AlGaN/GaN HEMTs with reduced on‐resistance
Authors: Nomoto Kazuki , Mishima Tomoyoshi , Satoh Masataka , Nakamura Tohru 
Published: June 2007

AbstractIncorporation of ion implantation to AlGaN/GaN high‐electron mobility transistor (HEMT) processing has been demonstrated. The source/drain regions formed using Si ion implantation into undoped AlGaN/GaN on sapphire substrate. Devices with gate length of 1 µm and source/drain distance of 5 µm were fabricated. In comparison with the conventional devices without ion‐implanted source/drain structures, the ion‐implanted devices showed excellent device performance. On‐resistance reduced from 10.2 to 4.0 Ω·mm. Saturation drain current and maximum transconductance increase from 600 to 1100 mA/mm and from 100 to 180 mS/mm, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of thick a‐plane GaN on r‐plane sapphire by direct synthesis method
Authors: Nishino K. , Sakamoto A. , Sakai S. 
Published: June 2007

AbstractThick film growth of nonpolar a‐plane GaN was carried out on r‐plane sapphire by direct synthesis method for a substrate of homoepitaxy of a‐plane GaN. A 30 μm thick a‐plane GaN film was obtained at growth temperature at 1050 °C with a low‐temperature buffer layer deposited at 700 °C. The surface was smooth but has some pits. Without a buffer layer, 20 μm thick a‐plane GaN with much fewer pits was obtained. The best FWHM of XRD peak in ω‐mode obtained was less than 700 arcsec. This film can be used as a substrate for a‐plane III‐nitrides growth.
Electroluminescence uniformity in green LEDs and dual color blue/green stacking LEDs
Authors: Onushkin Grigory , Lee Jinhyun , Yang Jung‐Ja , Lee Seong‐Suk , Lee In‐Chul , Kim Min‐Ho , Koike Masayoshi 
Published: June 2007

AbstractThe uniformity of Electroluminescence (EL) of green and blue/green stacking InGaN Light Emitting Diodes (LED) has been studied and analyzed by various techniques. Comparative measurements of Photo‐Luminescence (PL), Cathode‐Luminescence (CL) and EL allow us to conclude that non‐uniform distribution of EL in studied LEDs is caused by non‐uniformity of acceptors distribution over the p‐GaN area. It was found that there are some defective areas in p‐GaN having locally low level of acceptor concentration. These areas correspond to the surface hexagonal shaped pyramids on p‐GaN surface. The locally low doping level changes the field distribution, injection properties and the EL emission properties for these defective points. Optimization of p‐GaN growth conditions will improve the EL uniformity and increase the efficiency of green and blue/green LEDs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of Si+ implantation on reduction of contact resistance in Ti/Al contact to GaN
Authors: Satoh M. , Itoh N. , Nomoto K. , Nakamura T. , Mishima T. 
Published: June 2007

AbstractFor the Ti/Al contact to n‐type GaN, the impact of Si+ implantation on the reduction of contact resistance is investigated. The undoped GaN, grown on the sapphire substrate, is implanted by Si ions with the energy of 150 keV at the dose ranging from 5 x 1013 to 5 x 1014/cm2 and subsequently annealed at 1200 °C for 1 min in N2 gas flow. For the Ti(50 nm)/Al(200 nm) contacts annealed at 550 and 600 °C, as Si ion dose is increased, the specific contact resistance is decreased with the Schottky barrier height of 0.27 eV. The Ti/Al contact annealed at 600 °C reveals the exteremly low contact resistance as low as 1.2 x 10–7 Ωcm2 for the Si ion dose of 5 x 1014/cm2. Ti/Al contact annealed above 700 °C shows Rc in the order of 10–6 Ωcm2 even though Si ion dose increases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photo‐enhanced reactivation of Si donors deactivated by plasma‐induced defects in n‐type GaN
Authors: Nakamura Seiji , Ikadai Yuki , Suda Masayuki , Suhara Michihiko , Okumura Tsugunori 
Published: June 2007

AbstractThe behavior of plasma‐induced defects deactivating Si donors in GaN has been studied by using Schottky diodes with the UV illumination. It is interesting that the UV irradiating for the deactivated GaN leads to an enhancement of reactivation of the donors even at room temperature. It is found that the donor‐deactivated region in n‐GaN shifts toward the bulk region with increasing the illumination time. The effect of the UV illumination is thought to be the direct photodissociation of the donor‐defect complexes or the injection of holes as a minority carrier. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boron addition effects on aluminum nitride fabricated by radio‐frequency plasma‐assisted molecular beam epitaxy
Authors: Yamashita Masashi , Yoshiya Masato , Ishikawa Yukari , Ohsato Hitoshi , Shibata Noriyoshi 
Published: June 2007

AbstractBoron (B) added aluminum nitride (AlN) thin films have been fabricated by radio‐frequency plasma‐assisted molecular beam epitaxy and analyzed the effects of B addition to the AlN as a wide‐gap material. From first principles pseudo‐potential calculations, energy gap (Eg) of Al1‐xBxN at x = 0.25 obtained by a GGA exchange‐correlation term was estimated as 3.85 eV which is smaller than that of pure AlN. Refractive indices of AlBN (x = 0.29) measured by ellipsometry were smaller than those of pure AlN. Extinction coefficient of the Al1‐xBxN (x = 0.29) at 200 ‐ 500 nm increased by the B addition. The variation in the extinction coefficient can be explained by the decrease in calculated Eg. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Alloy composition fluctuation and band edge energy structure of In‐rich InxGa1–xN layers investigated by systematic spectroscopy
Authors: Ishitani Yoshihiro , Fujiwara Masayuki , Shinada Takuro , Wang Xinqiang , Che Son‐Bek , Yoshikawa Akihiko 
Published: June 2007

AbstractAfter the finding of the bandgap energy of InN as less than 1 eV, the re‐examination of the bandgap of InGaN alloys and its bowing parameter is an issue of interest. We study the absorption spectra of In‐rich InGaN layers by taking account of the Burstein‐Moss effect and bandgap renormalization with the analysis of photoluminescence and infrared reflectance spectra. We find the far larger broadening of optical transition and lattice vibration energies than those expected from the alloy composition fluctuation based on the x‐ray diffraction patterns. We estimate that local potential fluctuation by the alloy composition fluctuation give rise to the strong localization of carriers and relaxation of the momentum conservation rule in optical transition. The average bandgap energies of the films show the bowing parameter less than 1.4 eV; the value down to 0.7 eV is possible. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of AlGaN/InGaN/AlGaN heterostructure with selective area growth of Te‐doped AlGaN cladding layer grown by mixed‐source HVPE
Authors: Jang K. S. , Kim K. H. , Hwang S. L. , Jeon H. S. , Yang M. , Ahn H. S. , Kim S. W. , Honda Y. , Yamaguchi M. , Sawaki N. , Jang S. H. , Lee S. M. , Koike M. 
Published: June 2007

AbstractThe 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)
Effects of proton irradiation on electrical and optical properties of n‐InN
Authors: Emtsev V. V. , Davydov V. Yu. , Klochikhin A. A. , Sakharov A. V. , Smirnov A. N. , Kozlovskii V. V. , Wu C.‐L. , Shen C.‐H. , Gwo S. 
Published: June 2007

AbstractEffects of proton irradiation on the optical and electrical properties of n‐InN with charge carrier concentrations of 2 – 5 × 1018 cm–3 have been investigated. Strong changes in photoluminescence spectra and electrical parameters of irradiated n‐InN are discussed. Proton irradiation of n‐InN results in the appearance of shallow donors in large concentrations. Comparison with the effects observed on heavily degenerate n‐InN after proton irradiation leads to the conclusion that these irradiation‐produced donors are native defects, most likely vacancies on the nitrogen sublattice.
Dependence of In mole fraction in InGaN on GaN facets
Authors: Nakao K. , Li D. B. , Liu Y. H. , Miyake H. , Hiramatsu K. 
Published: June 2007

AbstractInGaN/GaN stripe structures and hexagonal pyramid structures were grown on sapphire (0001) by low‐pressure metalorganic vapor phase epitaxy (LP‐MOVPE). It was observed that the indium composition at (0001) was greater than that at {11$ \bar 2 $2}. For InGaN/GaN stripe and pyramid structures with {10$ \bar 1 $1}, the thickness, CL peak wavelength and CL intensity gradually increased from the bottom to the top of the facet. It is considered that this behavior on the facet is due to the indium diffusion mechanism or indium composition pulling effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensing dynamics and mechanism of a Pd/AlGaN/GaN Schottky diode type hydrogen sensor
Authors: Akazawa Masamichi , Hasegawa Hideki 
Published: June 2007

AbstractHydrogen sensing characteristics of surface‐controlled Pd/AlGaN/GaN Schottky diodes were investigated in air. Sensors showed high detection sensitivities and fast turn‐on and turn‐off characteristics. Sensing dynamics and mechanism were explained in terms of Schottky barrier height reduction due to hydrogen‐induced interface dipole. Here, the dipole formation is controlled by the Langmuir isotherm including an oxygen reaction, and current transport is due to thermionic field emission. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of high‐quality 1‐inch diameter AlN single crystal by sublimation method
Authors: Mizuhara N. , Miyanaga M. , Fujiwara S. , Nakahata H. , Kawase T. 
Published: June 2007

Abstract1‐inch diameter AlN single crystals with the thickness of 0.025–2 mm were grown on SiC substrates by the sublimation method. Crystalline qualities were evaluated by X‐ray diffraction and EPD measurements. The FWHM of X‐ray rocking curve for (0002) reflection was 281 arcsec with 1.2‐mm thick crystal and dislocation density measured by EPD was 1.6×106/cm2 with 0.8‐mm thick crystal. These results were well consistent with the dependence of those properties on the thickness of the crystal, which was found in our previous work on 10‐mm diameter crystals. According to this dependence, growing the thick AlN crystal on SiC substrates by the sublimation method is expected to lead to high‐quality free‐standing 1‐inch AlN substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bright electron emission from Si‐doped AlN thin films
Authors: Kishimoto A. , Inou Y. , Kita T. , Wada O. 
Published: June 2007

AbstractWe report the emission properties of the low temperature grown Si‐doped AlN thin films by reactive radio‐frequency magnetron sputtering technique. With increasing Si‐doping concentration, the emission characteristics have been improved. The low threshold electric field of 4.4 V/μm, and the saturation current density of 0.74 mA/cm2 has been obtained. According to analysis of the I‐V characteristics, it is found that the low effective work function causes the high emission performance. The luminance by using blue phosphor exceeds 700 cd/m2. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonpolar a‐ and m‐plane bulk GaN sliced from boules: structural and optical characteristics
Authors: Paskova T. , Kroeger R. , Hommel D. , Paskov P. P. , Monemar B. , Preble E. , Hanser A. , Williams N. M. , Tutor M. 
Published: June 2007

AbstractBulk GaN substrates grown by HVPE in the [0001] direction and sliced along the (11‐20) a‐plane and the (1‐100) m‐plane have been studied by SEM, TEM, HRXRD, CL and PL. Smooth morphology, low defect density, and narrow linewidths of the main XRD reflections and PL peaks are revealed and thus all the results demonstrate superior structural and optical quality of both a‐ and m‐plane bulk GaN material achieved by HVPE growth of boules in the conventional [0001] direction and subsequently sliced along nonpolar planes, implying the approach as the most promising to produce nonpolar GaN substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bending in HVPE grown GaN films: origin and reduction possibilities
Authors: Paskova T. , Becker L. , Böttcher T. , Hommel D. , Paskov P. P. , Monemar B. 
Published: June 2007

AbstractWe have studied the effects of film and substrate thicknesses on the bending and strain of thick GaN films grown by HVPE. Both experimental and simulation data, being in a very good agreement, show the highest bending at a critical film thickness slightly smaller than the substrate thickness, while the strain remains decreasing with only a small increase at much higher film thicknesses. Temperature dependent measurements allows a separation of the thermally induced component and an extrapolation of the bending to the growth temperature. The latter was found to be dependent on both the film and substrate thickness and to have a strong effect on the remaining bending of freestanding films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier transport studies of dichromatic InGaN‐based LEDs with spacer bandgap dependence
Authors: Feng Shih‐Wei , Pan C. C. , Chyi Jen‐Inn , Kuo Chien‐Nan , Chen Kuei‐Hsien 
Published: June 2007

AbstractCarrier transport of dichromatic InGaN‐based LEDs with AlGaN spacer bandgap dependence has been studied. TREL measurements show that carrier dynamics could be well explained by the combined effects of carrier effective mass, carrier mobility, quantum confinement, and device structures. The experimental results provide important information for device designs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of AlGaN/GaN MOSHFETs with Al2O3 as gate oxide
Authors: Gregušová D. , Stoklas R. , Čičo K. , Heidelberger G. , Marso M. , Novák J. , Kordoš P. 
Published: June 2007

AbstractWe report on AlGaN/GaN metal‐oxide‐semiconductor heterostructure field‐effect transistors (MOSHFETs) with MOCVD deposited Al2O3 as a gate oxide. Properties of MOSHFETs with 9 nm and 14 nm thick Al2O3 are compared with conventional HFETs prepared simultaneously on the same layer structure. Lower gate leakage current (∼10–5 A/mm at –10 V) and higher saturated drain current (up to 40%) are obtained for MOSHFETs than those for HFETs. In contradiction to previously reported data, the extrinsic transconductance for MOSHFETs is also higher (up to 37% of peak values) than that for HFET. This indicates on semi‐conductive rather than insulating properties of Al2O3 gate oxide. Pulsed I–V measurements (pulse width 1 µs) yielded lower but still measurable current collapse in MOSHFETs compared to HFETs. Nevertheless, obtained results show that Al2O3 gate oxide, after optimising its microstructure and thickness, can be preferable for the preparation of AlGaN/GaN MOSHFETs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)