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Luo W.,Peking University | Wu J.,Peking University | Goldsmith J.,Sino Nitride Semiconductor Ltd | Du Y.,Peking University | And 3 more authors.
Journal of Crystal Growth | Year: 2012

About 1.2 mm thick GaN bulk crystals were obtained by combining a pulsed NH 3-flow modulation (PFM) method and a self-separation method of short-shutting NH 3 flow when using hydride vapor phase epitaxy (HVPE). High crystal quality of bulk GaN was evaluated by X-ray rocking curves (XRC) and the full width at half maximum (FWHM) values were 110, 72 and 83 arcsec for (002), (102) and (100) reflection planes, respectively. The PFM method is proved to be effective in reducing cracks and keeping the surface smooth. And the method of short-shutting NH 3 flow can lead to GaN thick layer separate from sapphire substrate when cooling from the high growth temperature. Growth and separation mechanisms were investigated. Two states were found in PFM method. With PFM method modulating between high quality state and low stress state, 300 μm thick GaN layers without cracks were obtained. Study of spontaneous separation mechanism revealed that the separation attributed to formation of voids inside the GaN layer. © 2011 Elsevier B.V. All rights reserved. Source

Goldsmith J.,Sino Nitride Semiconductor Ltd | Du Y.-H.,Peking University | Wu J.-J.,Peking University | Luo W.-K.,Peking University | And 5 more authors.
Chinese Physics B | Year: 2011

Two strain-state samples of GaN, labelled the strain-relief sample and the quality-improved sample, were grown by hydride vapour phase epitaxy (HVPE), and then characterized by high-resolution X-ray diffraction, photoluminescence and optical microscopy. Two strain states of GaN in HVPE, like 3D and 2D growth modes in metal-organic chemical vapour deposition (MOCVD), provide an effective way to solve the heteroepitaxial problems of both strain relief and quality improvement. The gradual variation method (GVM), developed based on the two strain states, is characterized by growth parameters' gradual variation alternating between the strain-relief growth conditions and the quality-improved growth conditions. In GVM, the introduction of the strain-relief amplitude, which is defined by the range from the quality-improved growth conditions to the strain-relief growth conditions, makes the strain-relief control concise and effective. The 300-μm thick bright and crack-free GaN film grown on a two-inch sapphire proves the effectiveness of GVM. © 2011 Chinese Physical Society and IOP Publishing Ltd. Source

Zhao J.,Jiangsu University | Zuo R.,Jiangsu University | Liu P.,Peking University | Liu P.,Sino Nitride Semiconductor Ltd | And 4 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2015

In order to increase the susceptor temperature and the temperature uniformity for a large-scale hydride vapour phase epitaxy (HVPE) reactor, two-dimensional numerical modeling was performed for the flow and temperature fields in the HVPE reactor. The base modeling results show that, the heater near the vicinity of showerhead affects the susceptor temperature more than the heater near the bottom, and with increasing heater power the susceptor temperature uniformity is deteriorated. On the basis of the base modeling, adding Mo radiation shields at the reactor bottom to elevate the susceptor temperature was prepared. The optimized results show that, the susceptor temperature increases by about 48 K and the temperature uniformity changes little. In addition, a cylindrical slot was cut inside the susceptor with four pieces of Mo shields installed, and the uniformity of the susceptor temperature is optimized significantly, while the temperature is further elevated by about 5 K. ©, 2015, Chinese Ceramic Society. All right reserved. Source

Liu N.,Peiking University | Wu J.,Peiking University | Li W.,Sino Nitride Semiconductor Ltd | Luo R.,Peiking University | And 5 more authors.
Journal of Crystal Growth | Year: 2014

A new nozzle structure was developed in an improved multi-wafer hybrid vapor phase epitaxy (IHVPE) system by adding an inner dilution gas (ID) pipe between V and III groups gas channels. Experimental results showed that the thickness distribution of 2-inch GaN layer depended strongly on the flow rate of ID gas. The uniformity of film can arrive at ±3-4% by optimizing ID gas, which was better than that of ±30% grown in the old conventional multi-wafer hybrid vapor phase epitaxy (CHVPE) system. Meanwhile, the crystal quality and surface morphology were also greatly improved for GaN film by using the new reactor structure. The FWHM values of (002) and (102) were reduced from 342″ and 806″ to 207″ and 254″, respectively. AFM result of surface roughness (RMS, 10 μm×10 μm) of GaN layer was also lowered from 1.226 nm to 0.798 nm. It was partly because of the suppression of parasitic polycrystalline deposition due to the ID gas. This simple and economic method could provide an effective solution to simultaneously fabricate multiple GaN wafer with good thickness uniformity, high crystal quality and low cost. © 2013 The Authors. Source

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