Gang Seok Lee

The growth of GaN on the metallic compound graphite substrate by HVPE

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.

Mechanism of light emission and manufacturing process of vertical-type light-emitting diode grown by hydride vapor phase epitaxy

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.

Growth of AlN layer on patterned sapphire substrate by hydride vapor phase epitaxy

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.

AlN and AlGaN layers grown on Si(111) substrate by mixed-source hydride vapor phase epitaxy method

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.

Nonphosphor White Light Emitting Diodes by Mixed-Source Hydride Vapor Phase Epitaxy

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.

Growth of GaN on Metallic Compound Graphite Substrate Using Hydride Vapor Phase Epitaxy

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.

Ultraviolet Light Emitting Diode with High Quality Epilayer Grown by Hydride Vapor Phase Epitaxy

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.