Journal ArticleDOI
Dislocation mediated surface morphology of GaN
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In this article, the surface morphology of GaN films grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) was studied using atomic force microscopy (AFM).Abstract:
The surfaces of GaN films grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were studied using atomic force microscopy (AFM). Due to the high dislocation densities in the films (108 cm−2), the typical surface morphologies of layers grown by both techniques were dominated by three dislocation mediated surface structures—pinned steps, spiral hillocks, and surface depressions. The characteristics of these surface structures were found to depend on growth technique (MOCVD vs MBE) and the group-III to group-V ratio used in the growth of MBE GaN films. Pinned steps, created by the intersections of mixed character dislocations with the free surface, were found on all GaN films. The pinned steps were observed to be predominantly straight on the MOCVD GaN and curved into spiral hillock formations on the MBE GaN. Spiral growth hillocks form when pinned steps grow outward and around the dislocation under step-flow growth conditions. The tightness of the spiral hillocks on MBE G...read more
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High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels
TL;DR: In this paper, the authors combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage.
Journal ArticleDOI
Efficient dipole-dipole coupling of Mott-Wannier and Frenkel excitons in (Ga,In)N quantum well/polyfluorene semiconductor heterostructures
Grigorios Itskos,G. Heliotis,Pavlos G. Lagoudakis,John M. Lupton,N.P. Barradas,Eduardo Alves,Sérgio Pereira,Ian Watson,Martin D. Dawson,Jochen Feldmann,Ray Murray,Donal D. C. Bradley +11 more
TL;DR: In this paper, the authors investigate interactions between Mott-Wannier and Frenkel excitons in a family of hybrid structures consisting of thin organic (polyfluorene) films placed in close proximity (systematically adjusted by GaN cap layer thickness) to single inorganic quantum wells (QWs).
Journal ArticleDOI
Threading dislocations in epitaxial ferroelectric PbZr0.2Ti0.8O3 films and their effect on polarization backswitching
TL;DR: In this paper, the threading dislocations exhibited by PbZr0.2Ti0.8O3 films were investigated by cross-sectional and plan-view (high-resolution) transmission electron microscopy.
Journal ArticleDOI
Morphology evolution of ZnO(000 1̄) surface during plasma-assisted molecular-beam epitaxy
TL;DR: In this article, the morphology evolution of ZnO(000) surface during plasma-assisted molecular-beam epitaxy was studied, and the formation of hexagonal pits was attributed to the lack of surface mobility of adatoms.
Journal ArticleDOI
Effects of Threading Dislocation Density on the Gate Leakage of AlGaN/GaN Heterostructures for High Electron Mobility Transistors
Stephen W. Kaun,Man Hoi Wong,Sansaptak Dasgupta,Soojeong Choi,Roy B. Chung,Umesh K. Mishra,James S. Speck +6 more
TL;DR: In this paper, the effects of threading dislocation density on leakage through Schottky contacts on the AlGaN/GaN heterostructures were investigated under Ga-rich conditions by plasma-assisted molecular beam epitaxy.
References
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Journal ArticleDOI
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TL;DR: In this paper, it was shown that the rate of growth of a surface containing dislocations is proportional to the square of the supersaturation for low values and to the first power for high values of the latter.
Book
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Journal ArticleDOI
Role of threading dislocation structure on the x‐ray diffraction peak widths in epitaxial GaN films
B. Heying,X. H. Wu,Stacia Keller,Youli Li,D. Kapolnek,Bernd Keller,Steven P. DenBaars,James S. Speck +7 more
TL;DR: In this article, the authors demonstrate that the anomalously low (002) x-ray rocking curve widths for epitaxial hexagonal GaN films on (001) sapphire are a result of a specific threading dislocation geometry.
Book
Physics of Semiconductors and Their Heterostructures
TL;DR: In this article, the authors present a free electron picture of Crystalline Structures and a wave diffraction from Crystals, and then show how to use it for high field transport in Semiconductors.