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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.

High Al-composition AlGaN and AlN epilayers were grown directly on Si(111) substrate by a hydride vapor phase epitaxy (HVPE) method with a melted mixed source in a graphite boat set in a source zone with high temperatures of T = 700 and 800 °C, respectively. The presence of the Ga material in the mixed source of Ga and Al promoted the growth of AlN and AlGaN epilayers in the growth zone. When the temperature in the source zone was 800 °C, the crystalline quality of the AlN and AlGaN epilayers increased as the ratio of Ga to Al increased, and the optimum mix ratio of Ga to Al for the growth of AlN epilayers was approximately 0.35–0.42, obtained from a numerical fitting analysis of the X-ray diffraction (XRD) data for these epilayers. It appears that they can be grown directly by our melted-mixed-source HVPE method in a high-temperature source zone.

We developed a vertical-type light-emitting diode (LED) in which the substrate is removed using a hydride vapor phase epitaxy (HVPE) apparatus consisting of a multi-graphite boat filled with a mixed source and a high-temperature (T ≈ 900 °C) RF heating coil outside the source zone. The new chip-growth process with a significant reduction in the number of production steps is completed in only four steps, namely, photolithography, epitaxial layer growth, sorting, and metallization. We analyze the emission mechanism of these lights from measurement results to validate the characteristics of the light emitted from these vertical-type blue LEDs and white LEDs (WLEDs) without substrates, and propose that this mixed-source HVPE method may be a promising production technique for LEDs.

Even though a patterned sapphire substrate (PSS) has been used for the growth of a high-quality epilayer because of its many advantages, it has not been successfully used to grow an AlN epilayer for ultraviolet (UV) light-emitting diodes (LEDs) on a PSS up to now. We report the growth of a high-quality AlN epilayer on a PSS, as a substrate for the manufacture of UV LEDs, by hydride vapor phase epitaxy (HVPE). The X-ray diffraction (XRD) peaks for the AlN epilayer grown on the PSS indicate that crystalline AlN with a wurtzite structure was grown successfully on the PSS. Furthermore, HVPE combining both in situ HVPE technology and liquid-phase epitaxy (LPE) using a mixed source is proposed as a novel method for the growth of a flat AlN epilayer on a PSS.

The slope efficiency and threshold of neodymium doped lanthanum scandium borate, Nd3+:LaSc3(BO3)4 (Nd:LSB) microchip material was improved by changing the pumping wavelength from 807 nm to 884 nm. The direct pumping to the level of 4F3/2 instead of 4F5/2, a conventional pumping level, lessened thermal loading that leads to the thermo-optical problem and internal residual loss. The slope efficiency was increased from 55% to 59%, the threshold was lessened from 20 mW to 6 mW, and the estimated internal residual loss was from 1.68% to 0.72% with 10% Nd:LSB in optimum condition.

In this paper, the GaN poly crystal was grown by hydride vapor phase epitaxy at 1090 °C on the metallic compound graphite substrate with good heat dissipation. The coefficient of thermal expansion of the metallic compound graphite substrate is 6.2 µm/(m·K). The heat conductivity is 150 W/(m·K), and specific gravity is 3.1. The metallic compound graphite substrate was gained higher thermal conductivity more than the sapphire substrate through by injecting the nonferrous metal in the porosity carbon graphite base. The GaN poly crystal grown along the [0001] c-axis by hydride vapor phase epitaxy was observed on the metallic compound graphite substrate through the scanning electron microscope and energy dispersive spectroscopy. And electrical characteristic of substrate with each different condition was investigated by Hall Effect measurement.

We report on the growth and characterization of GaN rods selectively grown on the apex of hexagonal GaN pyramids. SiO2 near the apex of the hexagonal GaN pyramids was removed by an optimized photolithography process and subsequently subjected to Au deposition and selective growth of GaN rods by metal organic vapor phase epitaxy (MOVPE). It was observed that there were preferred GaN rods orientations toward directions. The GaN rods had triangular cross section enclosed with (1122), (1122), and (0001) side facets. A particular feature was that each rod has sharp edge at its very end. We found that the GaN rods could be formed not by vapor–liquid–solid (VLS) process but Ga–Au intermediate state. This work opens up new growth methods for position and density controlled III–nitride nano- and micro-structures which have potential use in high functional devices, such as field emitters and gas sensors.

In this paper, we approached a novel fabrication for non phosphor white light emitting diodes (LEDs) by the growth of AlGaN/InAlGaN double-hetero structures using by mixed-source hydride vapor phase epitaxy (HVPE) system with multi-sliding boat. It is unique crystal growth technology different from conventional HVPE and metal organic chemical vapor deposition (MOCVD) system using mixed metal source of aluminum, indium and gallium. The characterization of non phosphor white LEDs was examined by photoluminescence (PL) and electroluminescence (EL). The results of EL were found green and yellow emissions as spectrum peaks near 500, 550, and 610 nm definitely. The CIE chromaticity coordinates of white LEDs was measured at injection current 30 mA. Our results are nearly positions; at x = 0.28 and y = 0.31. Even though the LED needs more improved in optical properties, we demonstrated achieving phosphor-free solid-state white lighting.

We studied GaN nanorods grown by hydride vapour phase epitaxy processes to identify optimal growth conditions that yield nanorods appropriate for use in nanodevices. The growth temperature was varied over the range 625–670 °C, and the morphology of the samples changed with increasing growth temperature. GaN nanorods formed at growth temperatures of 645 °C on a Si(111) substrate. At a fixed growth temperature of 645 °C, the HCl:NH3 gas flow ratio was adjusted from 1:37 to 1:41. GaN nanorods with a small diameter of 26 nm formed at a HCl:NH3 ratio of 1:38. Individual GaN nanorods clearly grew along the axial direction, perpendicular to the substrate. Cathodoluminescence measurements at room temperature revealed a red shift as the acceleration energy was increased to 15 keV, possibly associated with the internal electric field.

In this paper, the selective area growth (SAG) of SAG-UV light-emitting diode (LED) was performed by mixed-source hydride vapor phase epitaxy (HVPE) with a multi-sliding boat system. The SAG-UV LED consists of a Si-doped GaN layer, an Si-doped AlGaN cladding layer, an AlGaN active layer, an Zn-doped AlGaN cladding layer, and a Zn-doped GaN capping layer. All of the epitaxial layers of LED structure were grown consecutively with a multi-sliding boat system. Room-temperature electroluminescence (EL) characteristics show an emission peak wavelength of 330 nm at room temperature. The aging test result of SAG-UV LED shows that the current was changed from 27.7 to 31.2 mA during 170 h at room temperature. At the current–voltage (I–V) measurement, the turn-on voltage of the SAG-UV LED is 3.5 V at room temperature. The value of the series resistance is about 200 Ω. We find that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of ultra-violet LEDs with high quality epi-layer.

We studied the crystallographic orientation of GaN nanostructures grown on Si(111) and Al2O3 substrates. We evaluated Zr metal as a novel alternative to conventional buffer layers such as AlN and ZnO. One-dimensional structures (nanorods and nanoneedles) were grown by hydride vapor phase epitaxy at 650 and 600 °C, and investigated using field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. FE-SEM images showed that the GaN nanorods had a uniform diameter along the growth direction. XRD results indicated that the nanostructures had a hexagonal crystal structure, and pole figure measurements revealed that GaN nanostructures grown on the Si(111) substrate had a stronger c-axis crystallographic orientation than those grown on the Al2O3 substrate.

High quality Al and Ga-codoped ZnO (AGZO) thin films were successfully deposited both on sapphire substrates and GaN-based light emitting diodes (LED) with a tunnel junction (TJ) layer by using the radio frequency magnetron sputtering technique at room temperature. The AGZO thin films grown on sapphire substrate showed high transparency (96.3% at 460 nm) and low resistivity (6.8 ×10-4 Ω cm). The AGZO thin films deposited on the GaN-based LED with a TJ layer exhibited weak ohmic behavior although it improved slightly with the annealing. The optical output power of the TJ GaN-based LED with an AGZO transparent conducting layer was about 12.6 mW at 20 mA, and the external quantum efficiency was 23.0%. These values are approximately 1.7 times larger than that of the TJ GaN-based LED with a conventional Ni/Au layer.

This study examines the cracking of GaN films grown on Si(111) substrates, with particular focus on the effect of the density of crack-initiating defects (CIDs) on the crack spacing. The relationship between the CID density and crack spacing was examined by comparing specimens of the same thickness and under the same stress but with different CID density. The CID density in the GaN layer was changed by varying the ion-implanted area using patterning prior to metal–organic chemical vapor deposition (MOCVD) growth. The crack spacing decreased with increasing CID density, but this effect could not be explained by the previous model. Therefore, a CID-density related factor, n d, was newly introduced to explain the crack spacing and film stress relationship.