Browsing by Author "Huang, Hsin-Hsiung"

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A Novel Technique for Growing Crack-Free GaN Thick Film by Hydride Vapor Phase Epitaxy
(2008-11-01)
Huang, Hsin-Hsiung
;
Chen, Kuei-Ming
;
Tu, Li-Wei
;
Chu, Ting-Li
;
Wu, Pei-Lun
To prevent the cracking of GaN thick films grown on a sapphire substrate by hydride vapor phase epitaxy (HVPE), a novel technique without complex processes is developed. By adding a temperature ramping step in the HVPE GaN epitaxy process, more than 300-mu m-thick high-quality crack-free GaN thick films on sapphire substrate can be obtained by this technique. After separation by a conventional laser-induced lift-off process, a 1.5 in. 300 mu m freestanding GaN wafer with a dislocation density of approximately 1 x 10(7) cm(-2) could be fabricated without any cracks. No additional designed-patterned or stress-reduced structures were applied in these samples to reduce the dislocation density and thermal stress. [DOI: 10.1143/JJAP.47.8394]
Comparison between extended microtunnels along different crystal orientations in GaN
(2008)
Wu, Pei-Lun
;
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
;
Liu, Po-Chun
;
Lai, Chih-Ming
Triangular prism-like extended microtunnels (EMTs) can be easily formed in specially designed cpitaxial lateral overgrowth GaN thick films by selective wet chemical etching in molten potassium hydroxide (KOH), In this study, extended microtunnels along the < 1100 > and the < 1120 > directions were fabricated and compared. If tunnels along the < 1100 > direction, the (1122) planes would be the etch stop plane. While the tunnels along < 1120 > direction, the etch stop plane would become to (1011) planes. The activation energies of wet chemical etch for the {1122} planes and the (1011) planes were determined to be 23.6 kcal/mol (1.02 eV) and 22.8 kcal/mol (0.99 eV) using Arrhenius plot. On the other hand, the etching depths of the tunnels along the < 1100 > direction were more than twice the depths of the tunnels along the < 1120 > direction during the same etching time. The highest etch rate of the tunnels along the axial direction can reach 1000 mu m/hr in < 1100 > direction, which is believed to be the highest etch rate of GaN ever reported. Additional crystal facet of m-plane in GaN was also observed in the sample with extended microtunnels along the < 1120 > direction. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Effective reduction of bowing in free-standing GaN by N-face regrowth with hydride vapor-phase epitaxy
(2009-05-01)
Chen, Kuei-Ming
;
Huang, Hsin-Hsiung
;
Kuo, Yi-Lin
;
Wu, Pei-Lun
;
Chu, Ting-Li
Free-standing GaN films prepared with hydride vapor-phase epitaxy (HVPE) technique usually show bowing resulting from the high densities of defects near the N-polar face after separation from the original substrates. To solve the problem, a simple technique has been developed. A GaN layer was regrown on the N-polar face of the free-standing GaN by HVPE. High-resolution X-ray diffraction (HRXRD) measurements were performed to compare the bowings among GaN films before laser lift-off (LLO), after LLO, and after regrowth. The apparent reductions of XRD full-width at half-maximum (FWHM), along with the increase of XRD peak intensity, after regrowth clearly demonstrate the effectiveness of this method to eliminate bowings of the free-standing GaN films. (C) 2009 Elsevier B.V. All rights reserved.
Etching method for nitride semiconductor
(2009-03-05)
Lee, Wei-I
;
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
The invention discloses etching method for the nitride semiconductor. Firstly dielectric layer is formed on gallium nitride. The line pattern or dot pattern is formed on the dielectric layer by using the exposure, development, and etching processes. The dielectric layer is used as the mask for the epitaxial lateral overgrowth of follow-up gallium nitride layer. The thick gallium nitride film is grown on the dielectric layer. Then the wet etching process is used to remove the dielectric layer, and the thick gallium nitride film on the dielectric layer is etched to form the specific shape as required.
Extended microtunnels in GaN prepared by wet chemical etch
(2006-11-13)
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
;
Lee, Chi-Ling
;
Lee, Shih-Chang
;
Lee, Wei-I
It is demonstrated in GaN that microtunnels extended beyond hundreds of microns can be easily achieved using wet chemical etch. To obtain this result, specially designed structures of GaN layers are first grown on sapphire substrates with metal-organic chemical vapor deposition and subsequently with hydride vapor phase epitaxy techniques. The prepared samples are then chemically etched in molten KOH. With the designed structure of GaN layers, extended microtunnels with triangular cross sections are formed. The crystallographic planes of the triangular bevels belong to the {11(2) over bar 2} family. The etch rate of the tunnel can be as high as 10 mu m/min at proper etching conditions. (c) 2006 American Institute of Physics.
High-Quality Free-standing GaN Thick-films Prepared by Hydride Vapor Phase Epitaxy using Stress Reducing Techniques
(2009)
Huang, Hsin-Hsiung
;
Lee, Wei-I
;
Chen, Kuei-Ming
;
Chu, Ting-Li
;
Wu, Pei-Lun
As one of the most mature techniques for manufacturing free-standing GaN substrates, hydride vapor phase epitaxy (HVPE) always encounters problems associated with residue thermal stress, such as GaN bending and cracking during and after growth. This work presents a patterning approach and a non-patterning approach to reduce stress in thick GaN films grown on sapphires by HVPE. The patterning approach, forming dot air-bridged structures, adopted standard photolithography to fabricate hexagonally aligned patterns of dots on GaN templates. Following HVPE growth, regular voids were formed and buried in the GaN thick-films. These voids helped to relax the stress in the GaN thick-films. In the non-patterning approach, thick GaN films were simply grown at a specially set sequence of ramping temperatures during HVPE growth without any patterned structure. This temperature-ramping technique, gives crack-free high-quality 2"-diameter GaN films, thicker than 250 mu m, on sapphires in high yields. These thick GaN films can be separated from sapphire using conventional laser-induced lift-off processes, which can be followed by subsequent HVPE regrowths. A 600 mu m-thick free-standing GaN films has a typical dislocation density of around 4x10(6) cm(-2) with a full width at half maximum (FWHM) in the high resolution X-ray diffraction (HRXRD) spectrum of GaN (002) of around 150 arcsec. The residual stress in the thick GaN films was analyzed by micro-Raman spectroscopy. The effectiveness of the patterning and the non-patterning techniques in reducing the strain in GaN films is discussed. The advantages and weaknesses of the patterning and the non-patterning techniques will be elucidated.
Preparation of extended microtunnels in GaN by wet chemical etching
(2007-06-01)
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
;
Lee, Wei-I
;
電子物理學系
;
Department of Electrophysics
Extended microtunnels with triangular cross sections are demonstrated in GaN layers on sapphire substrates. The depths of the tunnels can easily reach several hundred micrometers by using wet chemical etching. To obtain this result, patterned growth of specially designed GaN layers is carried out on sapphire substrates with metalorganic chemical vapor deposition and subsequently hydride vapor-phase epitaxy techniques. The prepared samples are then chemically etched in molten potassium hydroxide, and microtunnels with triangularly etched cross sections are formed. The planes of the triangular bevels belong to the {11 (2) over bar2} family. The etch rate of the tunnel can be as high as 10 mu m/min under proper etching conditions. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Self-separated freestanding GaN grown on patterned substrate by hydride vapor phase epitaxy
(2007)
Lai, Chih-Ming
;
Liu, Wen Yu
;
Tsay, Jenq-Dar
;
Liu, Po Chun
;
Guo, Yih-Der
A freestanding Gallium Nitride bulk is obtained without using laser lift-off technology. Two techniques such as mask-less ELOG and air-bridge structure are applied on patterned substrate. A self-separated result is successfully demonstrated by using mask-less ELOG and air-bridge structure. Due to the thermal coefficient of expansion (TCE) mismatch between the GaN layer and the non-native (foreign) substrate, separation happens during cooling down after HVPE growth. Both two structures successfully help to lift GaN off the substrate. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Strain-reduced GaN thick-film grown by hydride vapor phase epitaxy utilizing dot air-bridged structure
(2009-05-01)
Huang, Hsin-Hsiung
;
Chao, Chu-Li
;
Chi, Tung-Wei
;
Chang, Yu-Lin
;
Liu, Po-Chun
A 300 pm GaN thick-film, in diameter 1.5 in, was demonstrated without any crack by hydride vapor phase epitaxy (HVPE) growth. The technique used in relaxing the residual stress caused by differences of thermal expansion coefficients (TEC) and lattice constants between GaN and sapphire substrate to prevent GaN film from crack is called a dot air-bridged structure. After the laser lift-off process, 300-mu m-thick freestanding GaN wafer, in diameter 1.5 in, could be fabricated. The compressive stress in the dot air-bridged structure was measured by micro-Raman spectroscopy with the E(2)(high) phonon mode. The compressive stress could be reduced to as small as 0.04 GPa, which could prevent the crack during the epitaxial process for GaN growth by HVPE. It is important to obtain a large-area crack-free GaN thick-film, which can be used for fabricating freestanding GaN wafer. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Triangular extended microtunnels in GaN prepared by selective crystallographic wet chemical etching
(2008)
Huang, Hsin-Hsiung
;
Wu, Pei-Lun
;
Zeng, Hung-Yu
;
Liu, Po-Chun
;
Chi, Tung-Wei
Extended microtunnels with triangular cross sections in thick GaN films were demonstrated using wet chemical etching on specially designed epitaxial lateral overgrowth structures. For tunnels along the < 1 (1) over bar 00 > and < 11 (2) over bar0 > directions of GaN, the {11 (22) over bar} and {10 (11) over bar} facets are the etch stop planes with activation energies of 23 kcal/mol determined by wet chemical etching. The axial etching rate of the tunnels in the < 1 (1) over bar 00 > direction is twice as large than that along the < 11 (2) over bar0 > direction. The highest etching rate of the tunnels in the axial direction is 1000 mu m/h. (C) 2008 The Electrochemical Society.