scholarly journals Raman Analysis of E2 (High) and A1 (LO) Phonon to the Stress-Free GaN Grown on Sputtered AlN/Graphene Buffer Layer

2020 ◽  
Vol 10 (24) ◽  
pp. 8814
Author(s):  
Yu Zeng ◽  
Jing Ning ◽  
Jincheng Zhang ◽  
Yanqing Jia ◽  
Chaochao Yan ◽  
...  
Keyword(s):  
Buffer Layer ◽  
High Speed ◽  
Wide Band ◽  
Biaxial Stress ◽  
Buffer Layers ◽  
Monolayer Graphene ◽  
Wide Band Gap ◽  
High Quality ◽  
Information Interaction ◽  
Aln Buffer

The realization of high-speed and high-power gallium nitride (GaN)-based devices using high-quality GaN/Aluminum nitride (AlN) materials has become a hot topic. Raman spectroscopy has proven to be very useful in analyzing the characteristics of wide band gap materials, which reveals the information interaction of sample and phonon dynamics. Four GaN samples grown on different types of buffer layers were fabricated and the influence of graphene and sputtered AlN on GaN epitaxial layers were analyzed through the E2 (high) and A1 (LO) phonon. The relationship between the frequency shift of E2 (high) phonons and the biaxial stress indicated that the GaN grown on the graphene/sputtered AlN buffer layer was stress-free. Furthermore, the phonon lifetimes of A1 (LO) mode in GaN grown on graphene/sputtered AlN buffer layer suggested that carrier migration of GaN received minimal interference. Finally, the Raman spectra of graphene with the sputtered AlN interlayer has more disorder and the monolayer graphene was also more conducive to nucleation of GaN films. These results will have significant impact on the heteroepitaxy of high-quality thin GaN films embedded with a graphene/sputtered AlN buffer, and will facilitate the preparation of high-speed GaN-based optoelectronic devices.

Characterization of Gan/Sapphire Interface and the Buffer Layer by TEM/AFM

2001 ◽  
Vol 7 (S2) ◽  
pp. 330-331
Author(s):  
B. Shea ◽  
Q. Sun-Paduano ◽  
D. F. Bliss ◽  
M. C. Callahan ◽  
C. Sung
Keyword(s):  
Buffer Layer ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Wide Band ◽  
Buffer Layers ◽  
Organic Chemical ◽  
Wide Band Gap ◽  
Tem Analysis ◽  
Flow Rates ◽  
Device Applications

Interest in wide band gap III-V nitride semiconductor devices is increasing for optoelectronic and microelectronic device applications. to ensure the highest quality, TEM analysis can characterize the substrate and buffer layer interface. Measurements taken by TEM reveal the density of dislocations/cm2 and the orientation of Burger's vectors. This information allows for changes to be made in deposition rates, temperatures, gas flow rates, and other parameters during the processing.The GaN/sapphire samples grown at AFRL were produced in two consecutive steps, first to provide a thin buffer layer, and the other to grow a lum thick epitaxial film. Both growth steps were prepared using metallic organic chemical vapor deposition (MOCVD) in a vertical reactor. Buffer layers were prepared using a range of temperatures from 525 to 535°C and with a range of flow rates and pressures in order to optimize the nucleation conditions for the epitaxial films.

High-Resolution X-Ray Diffractometry Investigation of Interface Layers in GaN/AlN Structures Grown on Sapphire Substrates

2003 ◽  
Vol 10 (02n03) ◽  
pp. 513-517
Author(s):  
Stephen Mudie ◽  
Konstantin Pavlov ◽  
Michael Morgan ◽  
Masao Tabuchi ◽  
Yoshikazu Takeda ◽  
...  
Keyword(s):  
High Resolution ◽  
Process Analysis ◽  
Wide Band ◽  
Buffer Layers ◽  
Structural Quality ◽  
Reciprocal Space Mapping ◽  
Wide Band Gap ◽  
X Ray ◽  
Aln Buffer ◽  
Interface Layers

GaInN is an important wide band gap material with applications in short wavelength optoelectronic devices. The GaInN layer is often grown on a sapphire substrate, with low-temperature-deposited AlN and thick GaN used as buffer layers. The growth regime consists of many steps, each of which contributes to the overall properties of the device. The aim of our high-resolution X-ray diffraction experiments, conducted at the Photon Factory (Tsukuba, Japan), was to investigate the structural quality of the AlN buffer layer, which affects the final properties of the device. Reciprocal space mapping was used to study samples (having various layer thicknesses) from each stage of the growth process. Analysis of the experimental data provides parameters such as mosaic block dimensions and orientation, lattice strain distribution, and layer thickness.

Effects of the Sputtering Time of AlN Buffer Layer on the Quality of ZnO Thin Films

2014 ◽  
Vol 881-883 ◽  
pp. 1117-1121 ◽  
Author(s):  
Xiang Min Zhao
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
Rf Magnetron Sputtering ◽  
Buffer Layers ◽  
Zno Thin Films ◽  
Zno Films ◽  
Si Substrates ◽  
Atomic Force ◽  
Structure Morphology ◽  
Aln Buffer

ZnO thin films with different thickness (the sputtering time of AlN buffer layers was 0 min, 30 min,60 min, and 90 min, respectively) were prepared on Si substrates using radio frequency (RF) magnetron sputtering system.X-ray diffraction (XRD), atomic force microscope (AFM), Hall measurements setup (Hall) were used to analyze the structure, morphology and electrical properties of ZnO films.The results show that growth are still preferred (002) orientation of ZnO thin films with different sputtering time of AlN buffer layer,and for the better growth of ZnO films, the optimal sputtering time is 60 min.

scholarly journals GaN Based p-n Structures Grown on SiC Substrates

1996 ◽  
Vol 1 ◽  
Author(s):  
V.A. Dmitriev
Keyword(s):  
Band Gap ◽  
Bright Light ◽  
Wide Band ◽  
Injection Laser ◽  
Light Emitters ◽  
Wide Band Gap ◽  
High Quality ◽  
P Type

Wide band gap nitrides(InN, GaN, AlN) have been considered promising optoelectronics materials for many years [1]. Recently two main technological problems in the nitrides were overcome: (1)high quality layers has been grown on both sapphire and SiC substrates and(2) p-type GaN and AlGaN material has been obtained. These achievements resulted in the fabrication of bright light emitters in the violet, blue and green spectral regions [2].First injection laser has been demonstrated [3]. This paper reviews results obtained over the last few years on nitride p-n junctions, particularly on GaN based p-n junctions grown on SiC substrates. We will consider GaN p-n junctions, AlGaN p-n junctions, GaN and AlGaN p-i-n structures, and, finally, GaN/SiC p-n structures.

Epitaxial Growth of Aluminum Nitride on Sapphire and Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
K. Dovidenko ◽  
S. Oktyabrsky ◽  
J. Narayan ◽  
M. Razeghi
Keyword(s):  
Epitaxial Growth ◽  
Substrate Surface ◽  
Wide Band ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
High Quality ◽  
Microstructural Characteristics ◽  
X Ray ◽  
Si Substrates ◽  
Transmission Electron

ABSTRACTThe microstructural characteristics of wide band gap semiconductor, hexagonal A1N thin films on Si(100), (111), and sapphire (0001) and (10ī2) were studied by transmission electron microscopy (TEM) and x-ray diffraction. The films were grown by MOCVD from TMA1 + NH3 + N2 gas mixtures. Different degrees of film crystallinity were observed for films grown on α-A12O3 and Si substrates in different orientations. The epitaxial growth of high quality single crystalline A1N film on (0001) α-Al2O3 was demonstrated with a dislocation density of about 2*10 10cm−2 . The films on Si(111) and Si(100) substrates were textured with the c-axis of A1N being perpendicular to the substrate surface.

GaN ON SILICON SUBSTRATE WITH AlN BUFFER LAYER FOR UV PHOTODIODE

2012 ◽  
Vol 21 (01) ◽  
pp. 1250014 ◽  
Author(s):  
L. S. CHUAH ◽  
S. M. THAHAB ◽  
Z. HASSAN
Keyword(s):  
Schottky Barrier ◽  
Buffer Layer ◽  
Barrier Height ◽  
Silicon Substrate ◽  
Dark Current ◽  
Schottky Barrier Height ◽  
Buffer Layers ◽  
Current Ratio ◽  
Principal Mechanism ◽  
Aln Buffer

Nitrogen plasma-assisted molecular beam epitaxy (PAMBE) deposited GaN thin films on (111) n-type silicon substrate with different thickness AlN buffer layers are investigated and distinguished by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman scattering. The thickness of AlN buffer layer ranged from 200 nm to 300 nm. Besides that, the electrical characteristics of the GaN thin film for ultraviolet detecting utilizations are studied by calculating the photo current/dark current ratio on a metal-semiconductor-metal (MSM) photodiode with and without the illumination of Hg-lamp source. The devices have been tested over room temperature (RT). The photocurrent analysis, together with the study of Schottky barrier height (SBH) development, ascertain that the principal mechanism of photo transport is thermionic emission. The photocurrent value is rigorously dependent on Schottky barrier height. The GaN/AlN(200 nm)/n-Si MSM photodiode produces the highest photo/dark current ratio for the lowest strain that consists of the GaN film grown on the AlN (200 nm) buffer layer.

scholarly journals Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

1999 ◽  
Vol 4 (S1) ◽  
pp. 417-422 ◽  
Author(s):  
E. C. Piquette ◽  
P. M. Bridger ◽  
R. A. Beach ◽  
T. C. McGill
Keyword(s):  
Surface Morphology ◽  
Buffer Layer ◽  
Flux Ratio ◽  
Plasma Source ◽  
Growth Conditions ◽  
Nitrogen Plasma ◽  
Layer Growth ◽  
Buffer Layers ◽  
Flat Surfaces ◽  
Aln Buffer

The surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than 1 nm RMS.

Microstructures of AlN Buffer Layers for the Growth of GaN on (0001) Al2O3

1996 ◽  
Vol 449 ◽  
Author(s):  
M. Yeadon ◽  
W. Kim ◽  
A. E. Botchkarev ◽  
S. N. Mohammad ◽  
H. Morkoc ◽  
...  
Keyword(s):  
Lattice Mismatch ◽  
Wide Band ◽  
Buffer Layers ◽  
Initial Growth ◽  
Nitridation Time ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Aln Buffer ◽  
Nitride Layers

ABSTRACTIll-nitride semiconductors are emerging as highly promising candidates for the fabrication of wide band-gap electronic and opto-electronic devices. Sapphire ((α-A12O3) is currently one of the primary substrates of choice for the growth of GaN despite a large lattice mismatch. Significant improvements in the quality of III-nitride layers have been demonstrated by exposure of the substrate to reactive nitrogen species followed by deposition of a low temperature AIN or GaN buffer layer. In this paper we present a study of the evolution of the surface topography and defect microstructure of nitrided α-A12O3 substrates and AIN buffer layers deposited by reactive molecular beam epitaxy (RMBE). Their influence on the morphology and properties of GaN layers is also discussed. Both nitridation time and AIN deposit thickness were varied systematically, at different temperatures and buffer growth rates. The microstructures were characterized using the atomic force microscope (AFM) and transmission electron microscope (TEM). Initial growth studies are ideally suited to in-situ experiments, and further investigations are also in progress using a unique UHV TEM with the facility for in-situ RMBE.

Optical and structural studies of high-quality bulk-like GaN grown by HVPE on a MOVPE AlN buffer layer

2006 ◽  
Vol 21 (5) ◽  
pp. 702-708 ◽  
Author(s):  
D Gogova ◽  
D Siche ◽  
R Fornari ◽  
B Monemar ◽  
P Gibart ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Structural Studies ◽  
High Quality ◽  
Aln Buffer

Study of high quality AlN layers grown on Si(111) substrates by plasma-assisted molecular beam epitaxy

1997 ◽  
Vol 2 ◽  
Author(s):  
M. A. Sánchez-García ◽  
E. Calleja ◽  
E. Monroy ◽  
F. J. Sánchez ◽  
F. Calle ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Growth Conditions ◽  
Buffer Layers ◽  
Structural Quality ◽  
Half Maximum ◽  
High Quality ◽  
Force Microscopy ◽  
Aln Buffer ◽  
Xrd Techniques

High quality AlN layers with full widths at half maximum values of 10 arcmin and average surface roughness (rms) of 48Å were grown by molecular beam epitaxy on Si(111) substrates. A systematic study and optimization of the growth conditions was performed in order to use these AlN layers as buffers in the growth of GaN films. Atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques were employed to determine the surface and structural quality of the layers. Best AlN films were obtained at high substrate temperatures (Tsubs>900°C) and III/V ratios close to stoichiometry. Growth conditions with III/V ratios beyond stoichiometry (Al-rich) did not further improve the crystal quality. In these cases a higher substrate temperature is needed to prevent condensation of Al on the surface. GaN films with full width at half maximum of 10 arcmin and improved optical properties were grown on top of optimized AlN buffer layers.

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