Effect of Buffer Design on AlGaN/AlN/GaN Heterostrucutres by MBE

2003 ◽  
Vol 798 ◽  
Author(s):  
Gon Namkoong ◽  
W. Alan ◽  
A. S. Brown ◽  
M. Losurdo ◽  
M. M. Giangregorio ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Buffer Layer ◽  
Growth Conditions ◽  
Buffer Layers ◽  
Structural Quality ◽  
Epitaxial Layers ◽  
Etch Pit Density ◽  
Etch Pit ◽  
Sheet Charge ◽  
Aln Buffer

ABSTRACTThe effect of the buffer layers on the subsequent GaN epitaxial layers and electrical properties of AlGaN/AlN/GaN heterojunction structures nitrided at various temperatures was investigated. For AlN buffer layers, two different growth conditions of AlN buffer layers were introduced to avoid Al droplets. We found that etch pit density and structural quality of GaN epitaxial layer strongly depends on the growth conditions of AlN buffer layers. When using a double buffer layer (low temperature GaN on high temperature AlN) for 200 °C nitridation, the etch pit density was measured to high 107 cm-2 in GaN epitaxial layers. Furthermore, we observed that electrical properties of AlGaN/AlN/GaN heterostructures depend on growth conditions of buffer layers and nitridation temperatures. The mobility in Al0.33Ga0.67N/AlN/GaN structures grown on single AlN buffer layers for 200 °C nitridation were 1300 cm2/Vs at a sheet charge of 1.6×1013 cm-2. Using the double buffer layer for 200 °C nitridation, the mobility increased to 1587 cm2/Vs with a sheet charge of 1.25×1013 cm-2.

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.

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.

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

1998 ◽  
Vol 537 ◽  
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

AbstractThe 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 l nm RMS.

Study of Interface Properties of InN and InN-Based Heterostructures by Molecular Beam Epitaxy

2001 ◽  
Vol 693 ◽  
Author(s):  
Hai Lu ◽  
William J. Schaff ◽  
Lester F. Eastman ◽  
Colin Wood
Keyword(s):  
Molecular Beam Epitaxy ◽  
Film Thickness ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Growth Conditions ◽  
High Energy ◽  
Near Surface ◽  
Low Leakage ◽  
Sheet Charge ◽  
Aln Buffer

AbstractIn this work, we prepared epitaxial InN on (0001) sapphire with an AlN or GaN buffer layer by molecular beam epitaxy (MBE). A series of samples were grown with different thickness under the optimized growth conditions. Films were characterized by x-ray diffraction (XRD), reflective high-energy electron diffraction (RHEED), atomic-force microscopy (AFM), transmission electron microscopy (TEM) and Hall measurements. By extrapolating the fitted curve of sheet carrier density vs. film thickness to zero film thickness, a strong residual sheet charge was derived, which may be located at the interface between the buffer layer and the InN film, or at the near-surface. It was found that for InN film on AlN buffer, the residual sheet charge is about 4.3×1013 cm-2, while for InN films on GaN buffer, the residual sheet charge is about 2.5×1013 cm-2. At present, we tentatively believe that the residual charge is surface charge accumulation similar to what is observed at the InAs surface. InN samples with Hall mobility beyond 1300 cm2/Vs and carrier concentration below 2×1018 cm-3 were routinely achieved in this study.The first study on InN-based FET structures was performed. Amorphous AlN was used as the barrier material, which was prepared by migration enhanced epitaxy (MEE) at low growth temperature. It was found that the surface morphology is improved after an AlN barrier layer is added to InN. Hg was used as a back-to-back Schottky metallization. Very low leakage current and weak rectifying behavior were observed.

scholarly journals Growth Of High Quality GaN Thin Films By MBE On Intermediate-temperature Buffer Layers

2000 ◽  
Vol 5 (1) ◽  
Author(s):  
W.K. Fong ◽  
C. F. Zhu ◽  
B. H. Leung ◽  
Charles Surya
Keyword(s):  
Low Temperature ◽  
Buffer Layer ◽  
Electron Mobility ◽  
Unique Feature ◽  
Growth Conditions ◽  
Intermediate Temperature ◽  
Buffer Layers ◽  
Rf Plasma ◽  
Epitaxial Layers ◽  
High Quality

We report the growth of high quality GaN epitaxial layers by rf-plasma MBE. The unique feature of our growth process is that the GaN epitaxial layers are grown on top of a double layer that consists of an intermediate-temperature buffer layer (ITBL), which is grown at 690°C and a conventional low-temperature buffer layer deposited at 500°C. It is observed that the electron mobility increases steadily with the thickness of the ITBL, which peaks at 377 cm2V−1s−1 for an ITBL thickness of 800 nm. The PL also demonstrated systematic improvements with the thickness of the ITBL. Our analyses of the mobility and the photoluminescence characteristics demonstrate that the utilization of an ITBL in addition to the conventional low-temperature buffer layer leads to the relaxation of residual strain within the material resulting in improvement in the optoelectronic properties of the films. A maximum electron mobility of 430 cm2V−1s−1 can be obtained using this technique and further optimizing the growth conditions for the low-temperature buffer layer.

Investigation of In-Grown Dislocations in 4H-SiC Epitaxial Layers

2006 ◽  
Vol 527-529 ◽  
pp. 147-152 ◽  
Author(s):  
Kazutoshi Kojima ◽  
Tomohisa Kato ◽  
Satoshi Kuroda ◽  
Hajime Okumura ◽  
Kazuo Arai
Keyword(s):  
Epitaxial Growth ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
Growth Conditions ◽  
Epitaxial Layers ◽  
Etch Pit Density ◽  
High Conversion Efficiency ◽  
Etch Pit ◽  
Edge Dislocations

We have investigated the generation of new dislocations during the epitaxial growth of 4H-SiC layers. Dislocations were mainly propagated from the substrate into the epitaxial layer. However, it was found that some amount of new threading edge dislocations (TEDs) and basal plane dislocations (BPDs) were generated during the epitaxial growth. The generation of those dislocations appeared to depend on the in-situ H2 etching conditions, not the epitaxial growth conditions. By optimizing in-situ H2 etching condition, we were able to effectively suppress the generation of new dislocations during epitaxial growth, and obtain 4H-SiC epitaxial layers which have the equivalent etch pit density (EPD) to the substrates. Our additional investigation of the conversion of BPDs to TEDs revealed that its efficiency similarly depends on in-situ H2 etching. We were able to obtain a high conversion efficiency of 97 % by optimizing the in-situ H2 etching conditions before epitaxial growth.

Effect of Aluminum Nitride Buffer Layer Temperature on Gallium Nitride Grown by OMVPE

1994 ◽  
Vol 339 ◽  
Author(s):  
L. B. Rowland ◽  
K. Doverspike ◽  
D. K. Gaskill ◽  
J. A. Freitas
Keyword(s):  
Gallium Nitride ◽  
Buffer Layer ◽  
Growth Temperature ◽  
Growth Conditions ◽  
Layer Growth ◽  
Buffer Layers ◽  
Double Crystal ◽  
Relative Crystallinity ◽  
Excitonic Emission ◽  
Aln Buffer

ABSTRACTGallium nitride layers were grown by organometallic vapor phase epitaxy on AlN buffer layers deposited in the range of 450–650°C. The GaN growth conditions were kept constant so that changes in film properties were due only to changes in the buffer layer growth temperature. A monotonie improvement in relative crystallinity as measured by double-crystal X-ray diffraction corresponded with a decrease in buffer layer growth temperature. Improvements in GaN electron transport at 300 and 77 K were also observed with decreasing AlN buffer layer temperature. Photoluminescence spectra for the lowest temperatures studied were dominated by sharp excitonic emission, with some broadening of the exciton linewidth observed as the buffer layer growth temperature was increased. The full width at half maximum of the excitonic emission was 2.7 meV for GaN grown on a 450°C buffer layer. These results indicate that minimizing AlN buffer layer temperature results in improvements in GaN film quality.

Study of the growth mechanism and properties of InN films grown by MOCVD

2003 ◽  
Vol 798 ◽  
Author(s):  
Abhishek Jain ◽  
Joan M. Redwing
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
Growth Temperature ◽  
Room Temperature ◽  
Growth Conditions ◽  
Buffer Layers ◽  
Film Morphology ◽  
Buffer Layer Thickness ◽  
Aln Buffer

ABSTRACTThin films of InN were grown on (0001) Sapphire by MOCVD. The effect of growth conditions and buffer layer on the film morphology was studied. Growth temperature and TMI flow rate were important factors in the growth of InN. The use of a low temperature AlN buffer layer was also found to improve the morphology and crystal quality of the films. Thin (<40Å) AlN buffer layers produced the best results while polycrystalline InN was obtained when the buffer layer thickness exceeded 60Å. Delamination of the InN films was observed to occur at growth temperature, which limited the thickness of the films to less than 300 nm. A room temperature mobility of 792 cm2/Vs and an electron concentration of 2.1×1019 cm-3 were measured in an approximately 200 nm thick InN layer grown on sapphire.

scholarly journals Structural properties of MOVPE GaN layers grown by a new multi-buffer aproach

1998 ◽  
Vol 3 ◽  
Author(s):  
J. Kozlowski ◽  
R. Paszkiewicz ◽  
R. Korbutowicz ◽  
M. Panek ◽  
B. Paszkiewicz ◽  
...  
Keyword(s):  
High Temperature ◽  
Electrical Properties ◽  
Buffer Layer ◽  
Growth Conditions ◽  
Optical Microscope ◽  
Lattice Parameter ◽  
Layer Growth ◽  
Buffer Layers ◽  
Molar Ratio ◽  
X Ray

GaN undoped layers of good morphology, good crystallinity and electrical properties were grown on c-plane sapphire substrates by the atmospheric pressure MOVPE technique using a new multi-buffer growth approach. A suitable buffer layer growth technique was worked out which enabled growth of GaN layers with properties superior to those grown in a conventional process scheme. Additional buffer layers, deposited with increasing temperature and increasing V/III molar ratio, were inserted between the low temperature buffer layer and the high temperature GaN layer grown on it. The c and a lattice constants of the high temperature GaN overgrown layer were evaluated from X-ray data. The layer mosaicity and c-lattice parameter variation were determined. The relationship between c and a lattice parameters and the second buffer layer growth scheme has been studied. The effect of second buffer layer growth conditions, buffer layer annealing time as well as the influence of V/III molar ratio during the high temperature GaN deposition on the crystalline and electrical properties of overgrown GaN epitaxial layers are presented. Characterization includes surface morphology examination by SEM and Nomarski optical microscope, X-ray diffraction and C-V measurements.

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.

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