Microstructure of epitaxial AlN layers on sapphire substrates deposited by physical vapor deposition

2013 ◽  
Vol 1492 ◽  
pp. 129-134
Author(s):  
Sandeep Kohli ◽  
Boris Druz ◽  
Adrian Devasahayam ◽  
Arindom Datta ◽  
Frank Cerio
Keyword(s):  
Sapphire Substrate ◽  
Physical Vapor Deposition ◽  
Film Growth ◽  
Sapphire Substrates ◽  
Aln Film ◽  
Dislocation Densities ◽  
Out Of Plane ◽  
20 Nm ◽  
Edge Dislocations

ABSTRACTAsymmetric (10L) XRD peaks have been employed as a measure of epitaxial quality for aluminum nitride (AlN) nucleation layers (NL) deposited on sapphire substrate. Epitaxial AlN films have been deposited on 2-6” sapphire substrate by reactive sputtering. FWHM of AlN (103) and (105) were found to be an excellent indicator of quality of AlN films for GaN growth. AlN films produced nucleation layers with highly reproducible microstructure and GaN film growth. NLs had in-plane and out-of-plane texture as evident by the pole-figure results and selected area diffraction pattern. Based on electron microscopy results, AlN film thickness for complete atomic ordering was estimated to be 6-7 nm and most of the edge dislocations were seen in the first 20 nm of the film. Excellent thickness and texture uniformity were seen on planar and patterned sapphire substrates. A compressive stress of 2.9±0.2 GPa was seen in our BKM films. The maximum screw and edge dislocation densities of films were found to be ∼3 x 108 cm−2 and ∼9 x 109 cm−2 respectively. The root mean square roughnesses of A-polar films were found to be < 0.3 nm.

scholarly journals Heteroepitaxial Growth of High-Quality and Crack-Free AlN Film on Sapphire Substrate with Nanometer-Scale-Thick AlN Nucleation Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1634 ◽  
Author(s):  
Zhao ◽  
Hu ◽  
Lei ◽  
Wan ◽  
Gong ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Optical Transmittance ◽  
Ex Situ ◽  
Nanometer Scale ◽  
High Quality ◽  
Nucleation Layer ◽  
Light Emitting ◽  
Sapphire Substrates ◽  
Aln Film ◽  
Duv Led

High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation layer (NL). Three kinds of nanometer-scale-thick AlN NLs, including in situ low-temperature AlN (LT-AlN) NL, oxygen-undoped ex situ sputtered AlN NL, and oxygen-doped ex situ sputtered AlN NL, were prepared for epitaxial growth of AlN films on sapphire substrates. The influence of nanoscale AlN NL thickness on the optical transmittance, strain state, surface morphology, and threading dislocation (TD) density of the grown AlN film on sapphire substrate were carefully investigated. The average optical transmittance of AlN film on sapphire substrate with oxygen-doped sputtered AlN NL was higher than that of AlN films on sapphire substrates with LT-AlN NL and oxygen-undoped sputtered AlN NL in the 200–270 nm wavelength region. However, the AlN film on sapphire substrate with oxygen-undoped sputtered AlN NL had the lowest TD density among AlN films on sapphire substrates. The AlN film on sapphire substrate with the optimum thickness of sputtered AlN NL showed weak tensile stress, a crack-free surface, and low TD density. Furthermore, a 270-nm AlGaN-based DUV LED was grown on the high-quality and crack-free AlN film. We believe that our results offer a promising and practical route for obtaining high-quality and crack-free AlN film for DUV LED.

Grinding Performance Evaluation of the Developed Chemo-Mechanical Grinding (CMG) Tools for Sapphire Substrate

2012 ◽  
Vol 565 ◽  
pp. 105-110 ◽  
Author(s):  
Zhi Gang Dong ◽  
Shang Gao ◽  
P. Zhou ◽  
Ren Ke Kang ◽  
Dong Ming Guo
Keyword(s):  
Surface Roughness ◽  
Performance Evaluation ◽  
Surface Quality ◽  
Sapphire Substrate ◽  
Physicochemical Characteristics ◽  
Diamond Wheel ◽  
Mechanical Grinding ◽  
Sapphire Substrates ◽  
Grinding Performance

In order to improve the surface quality of sapphire substrates ground by diamond wheel, the chemo-mechanical grinding (CMG) tools for sapphire grinding was investigated in this paper. According to the processing principle of CMG, three CMG tools with different abrasives of SiO2, Fe2O3 and MgO were developed respectively. The compositions of the CMG tools were designed and optimized based on the physicochemical characteristics of sapphire. The grinding experiments were performed with the developed CMG tools and the grinding performance of three kind of tools were evaluated by comparing the surface roughness and the MRR of sapphire. The experiment results show that the grinding performance of SiO2 CMG tool was worst. The surface roughness and MRR corresponding to SiO2 CMG tool were all significantly poorer than Fe2O3 and MgO CMG tools. The highest MRR could be obtained by Fe2O3 CMG tool, but the best surface quality was obtained by MgO CMG tool.

scholarly journals Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1299
Author(s):  
Andreea Bianca Serban ◽  
Vladimir Lucian Ene ◽  
Doru Dinescu ◽  
Iulia Zai ◽  
Nikolay Djourelov ◽  
...  
Keyword(s):  
High Resolution ◽  
Diffusion Length ◽  
X Ray Diffraction ◽  
Correlation Lengths ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Elemental Diffusion ◽  
20 Nm ◽  
The Relationship

Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR-TEM). In addition, the dislocation densities together with the defect correlation lengths are investigated via High-Resolution X-ray Diffraction (HR-XRD) and the characteristic positron diffusion length is achieved by Doppler Broadening Spectroscopy (DBS). Moreover, a comparative analysis with our previous work (i.e., GaN/AlN/Si and GaN/AlN/Al2O3) has been carried out. Within the epitaxial GaN layer defined by the relationship (111) 3C-SiC || (0002) AlN || (0002) GaN, the total dislocation density has been assessed as being 1.47 × 1010 cm−2. Compared with previously investigated heterostructures (on Si and Al2O3 substrates), the obtained dislocation correlation lengths (Le = 171 nm and Ls =288 nm) and the mean distance between two dislocations (rd = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements upheld the aforementioned results with a higher effective positron diffusion length = 75 ± 20 nm for the GaN layer.

scholarly journals Effect of Top-Region Area of Flat-Top Pyramid Patterned Sapphire Substrate on the Optoelectronic Performance of GaN-Based Light-Emitting Diodes

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Hsu-Hung Hsueh ◽  
Sin-Liang Ou ◽  
Yu-Che Peng ◽  
Chiao-Yang Cheng ◽  
Dong-Sing Wuu ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Light Emitting Diodes ◽  
Light Extraction ◽  
Light Extraction Efficiency ◽  
X Ray Diffraction ◽  
Patterned Sapphire Substrate ◽  
Light Emitting ◽  
Sapphire Substrates ◽  
Patterned Sapphire Substrates

The flat-top pyramid patterned sapphire substrates (FTP-PSSs) have been prepared for the growth of GaN epilayers and the fabrication of lateral-type light-emitting diodes (LEDs) with an emission wavelength of approximately 470 nm. Three kinds of FTP-PSSs, which were denoted as FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C, respectively, were formed through the sequential wet etching processes. The diameters of circle areas on the top regions of these three FTP-PSSs were 1, 2, and 3 μm, respectively. Based on the X-ray diffraction results, the full-width at half-maximum values of rocking curves at (002) plane for the GaN epilayers grown on conventional sapphire substrate (CSS), FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 412, 238, 346, and 357 arcsec, while these values at (102) plane were 593, 327, 352, and 372 arcsec, respectively. The SpeCLED-Ratro simulation results reveal that the LED prepared on FTP-PSS-A has the highest light extraction efficiency than that of the other devices. At an injection current of 350 mA, the output powers of LEDs fabricated on CSS, FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 157, 254, 241, and 233 mW, respectively. The results indicate that both the crystal quality of GaN epilayer and the light extraction of LED can be improved via the use of FTP-PSS, especially for the FTP-PSS-A.

Effects of Sapphire Substrate Configurations on MBE Growth of ZnO

1999 ◽  
Vol 587 ◽  
Author(s):  
Keiichiro Sakurai ◽  
Ken Nakahara ◽  
Tetsuhiro Tanabe ◽  
Shizuo Fujita ◽  
Shigeo Fujita
Keyword(s):  
Surface Morphology ◽  
Sapphire Substrate ◽  
Film Growth ◽  
Semiconductor Devices ◽  
Optical Characteristics ◽  
Zno Films ◽  
Zno Film ◽  
Mbe Growth ◽  
Sapphire Substrates ◽  
Sensitive Factor

AbstractMBE growth of ZnO films for optical semiconductor devices was investigated on off-angled c-plane sapphire substrates. Twin crystal RHEED patterns and surface facetting observed with c-plane just-oriented substrates were suppressed by enlarging the offset angles from near-zero to 2.87 degrees. Though no significant changes were seen in optical characteristics, FWHM of XRC narrowed and surface morphology improved with larger offset angles, indicating that the offset angle is also a sensitive factor for ZnO film growth.

Hydride precipitation in vapor deposited Ti thin films

1993 ◽  
Vol 8 (2) ◽  
pp. 291-296 ◽  
Author(s):  
S.R. Peddada ◽  
I.M. Robertson ◽  
H.K. Birnbaum
Keyword(s):  
Thin Films ◽  
Crystal Structures ◽  
Sapphire Substrate ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Tetragonal Structure ◽  
Hydrogen Atoms ◽  
Sapphire Substrates ◽  
Face Centered ◽  
Habit Planes

Titanium hydrides having two different crystal structures were observed in α–Ti thin films grown epitaxially on sapphire substrates by e-beam physical vapor deposition. One of the hydrides (γ-hydride) had a face-centered tetragonal structure (c/a > 1) with an ordered arrangement of hydrogen atoms. The second hydride formed was the fcc δ-hydride. The γ-hydride grew as platelets in the α–Ti lattice with {10$\overline 1$0}Ti habit planes, whereas the γ-hydrides formed directly on the sapphire substrate parallel to the (0001)Ti. These hydrides are one of the principal causes of film decohesion.

Influence of Mis-Orientation of C-plane Sapphire Substrate on the Early Stages of MOCVD Growth of GaN Thin Films

2004 ◽  
Vol 831 ◽  
Author(s):  
Seong-woo Kim ◽  
Hideo Aida ◽  
Toshimasa Suzuki
Keyword(s):  
Thin Films ◽  
Sapphire Substrate ◽  
Orientation Angle ◽  
Rocking Curve ◽  
Sapphire Substrates ◽  
Early Stages ◽  
Mocvd Growth ◽  
The Difference ◽  
Afm Observation

ABSTRACTWe have studied the early stages of GaN growth to realize the growth mechanism of GaN thin films on mis-oriented sapphire substrates which affects the surface and crystal quality of GaN thin films. As the result, it was found that the larger mis-orientation angle helps the growth of the larger grain of GaN and leads to the earlier shift of growth mode from 3D to 2D. The AFM observation of closed-coalesced GaN thin films revealed the difference in the micro-step structures by the mis-orientation angle of sapphire substrate. The result of x-ray rocking curve as a function of mis-orientation angle well matched with the microstructure of GaN surface, indicating that the larger mis-orientation angle helps the column ordering of GaN crystals.

Growth of Ti thin films on sapphire substrates

1997 ◽  
Vol 12 (7) ◽  
pp. 1856-1865 ◽  
Author(s):  
S. Rao Peddada ◽  
I. M. Robertson ◽  
H. K. Birnbaum
Keyword(s):  
Thin Films ◽  
Physical Vapor Deposition ◽  
Single Phase ◽  
Epitaxial Relationship ◽  
X Ray ◽  
Sapphire Substrates ◽  
Titanium Thin Films ◽  
Sapphire Single Crystal ◽  
20 Nm ◽  
Ti Films

Titanium thin films have been grown by electron-beam physical vapor deposition on the (0001) surface of sapphire (single crystal α−Al2O3) substrates at growth temperatures ranging from 295 to 1223 K. Single phase α−Ti films grew at all growth temperatures, even at 1223 K which is above the α-β transition temperature of Ti. Crystal quality, as measured by the width of x-ray rocking curves, was found to improve, and the elastic strain to increase, as the growth temperature increased from 295 K to 1023 K. The epitaxial relationship between the Ti and sapphire was (0002)Ti ‖ (0006)Al2O3 and [1120]Ti ‖ [1010]Al2O3. The extent of interdiffusion across the Ti/Al2O3 interface was observed to be small (< 20 nm) at all growth temperatures.

The annealed (0001) α-alumina surface and its influence on thin-film growth

1995 ◽  
Vol 53 ◽  
pp. 336-337
Author(s):  
Michael W. Bench ◽  
Paul G. Kotula ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Surface Energy ◽  
Film Growth ◽  
Thin Film Growth ◽  
Energy Calculations ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Low Energy Electron ◽  
Surface Nature

The growth of semiconductors, superconductors, metals, and other insulators has been investigated using alumina substrates in a variety of orientations. The surface state of the alumina (for example surface reconstruction and step nature) can be expected to affect the growth nature and quality of the epilayers. As such, the surface nature has been studied using a number of techniques including low energy electron diffraction (LEED), reflection electron microscopy (REM), transmission electron microscopy (TEM), molecular dynamics computer simulations, and also by theoretical surface energy calculations. In the (0001) orientation, the bulk alumina lattice can be thought of as a layered structure with A1-A1-O stacking. This gives three possible terminations of the bulk alumina lattice, with theoretical surface energy calculations suggesting that termination should occur between the Al layers. Thus, the lattice often has been described as being made up of layers of (Al-O-Al) unit stacking sequences. There is a 180° rotation in the surface symmetry of successive layers and a total of six layers are required to form the alumina unit cell.

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