Characterization of Quantum well Structures Using Microscope-Spectrophotometry

1993 ◽  
Vol 324 ◽  
Author(s):  
Rachel M Geatches ◽  
Karen J Reeson ◽  
Alan J Criddle ◽  
Roger P Webb
Keyword(s):  
Quantum Wells ◽  
Spectral Reflectance ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Measurement Range ◽  
Aluminium Content ◽  
Quantum Well Structures ◽  
Nondestructive Characterization ◽  
Reflectance Measurements

AbstractIn this paper the application of microscope-spectrophotometry to the nondestructive characterization of a variety of multi-layer GaAs/A1GaAs structures, is described. Spectral reflectance results are used to indirectly determine variations in aluminium content, and the interdependency of aluminium content with layer thicknesses. The penetration depth of light from the visible spectrum is assessed from the correlation between spectral reflectance measurements and fitted optical models. Finally, a series of single quantum wells are investigated, and it is concluded that a significant improvement in the characterization of these materials will be achieved with an extension of the spectral measurement range into the ultra violet.

Cathodoluminescence characterization of two-dimensional interface structure of quantum wells

1990 ◽  
Vol 48 (4) ◽  
pp. 754-755
Author(s):  
Kazumi Wada
Keyword(s):  
Quantum Wells ◽  
Optical Transition ◽  
Two Dimensions ◽  
Interface Roughness ◽  
Luminescence Spectroscopy ◽  
Two Dimensional ◽  
Quantum Well Structures ◽  
Interface Structures ◽  
Nondestructive Characterization

Exotic properties shown by quantum well structures, typical structures of future electron devices, are sensitive to interface roughness. Extensive studies are, thus, focused on characterization of interface structures. Recent improvement in quantum wire fabrication technology demands for characterizing not only perpendicular-interfaces to the growth direction but also parallel-ones (sidewall-interfaces). Such sophistication needs innovation in two-dimensional and nondestructive characterization technology.In device structures, interfaces are generally located deep in bulk. STM which visualize surface atoms can not monitor such interface. It is, thus, difficult to two- dimensionally characterize the interfaces.Interface steps induce well width fluctuation, which modulates optical transition energy between ground subbands in conduction and valence bands. Thus, interface step structures can be characterized by luminescence spectroscopy. Cathodoluminescence basically meets demand for nondestructive characterization of interface structures in two dimensions.

Interface-Related In-Plane Optical Anisotropy of Quantum Wells Studied by Reflectance-Difference Spectroscopy

2005 ◽  
Vol 475-479 ◽  
pp. 1777-1782
Author(s):  
Y.H. Chen ◽  
X.L. Ye ◽  
Bo Xu ◽  
Yi Ping Zeng ◽  
Z.G. Wang
Keyword(s):  
Quantum Wells ◽  
Optical Anisotropy ◽  
Interface Roughness ◽  
Difference Spectroscopy ◽  
Quantum Well Structures ◽  
Semiconductor Interfaces ◽  
Atomic Segregation ◽  
Reflectance Difference Spectroscopy ◽  
Transition Index

The in-plane optical anisotropy of three groups of GaAs/AlGaAs quantum well structures has been studied by reflectance-difference spectroscopy (RDS). For GaAs/Al0.36Ga0.64As single QW structures, it is found that the optical anisotropy increases quickly as the well width is decreased. For an Al0.02Ga0.98As/AlAs multiple QW with a well width of 20nm, the optical anisotropy is observed not only for the transitions between ground states but also for those between the excited states with transition index n up to 5. An increase of the anisotropy with the transition energy, or equivalently the transition index n, is clearly observed. The detailed analysis shows that the observed anisotropy arises from the interface asymmetry of QWs, which is introduced by atomic segregation or anisotropic interface roughness formed during the growth of the structures. More, when the 1 ML InAs is inserted at one interface of GaAs/AlGaAs QW, the optical anisotropy of the QW can be increased by a factor of 8 due to the enhanced asymmetry of the QW. These results demonstrate clearly that the RDS is a sensitive and powerful tool for the characterization of semiconductor interfaces.

Characterization of III-V Semiconductor Structures Using Electron Beam Electroreflectance (EBER) spectroscopy.

1988 ◽  
Vol 144 ◽  
Author(s):  
M. H. Herman ◽  
I. D. Ward ◽  
S. E. Buttrill ◽  
G. L. Francke
Keyword(s):  
Electron Beam ◽  
Quantum Well ◽  
Quantum Wells ◽  
Sample Surface ◽  
Band Gap Energy ◽  
Quantum Well Structures ◽  
Resonant States

ABSTRACTEBER is a form of modulated reflectance spectroscopy in which a low energy electron beam alters the sample surface potential. For III-V semiconductors, the spectra are characteristic of electroreflectance, including excitonic, interband, and impurity transitions. The study of these transitions provides accurate estimations of band gaps in bulk and thick film samples. Measurements of the band gap energy in compounds such as AlxGa1-xAs provide highly precise evaluations of their composition.Additionally, EBER spectra of quantum well structures and heterojunctions provide useful information about the composition and quality of materials and interfaces. For quantum wells, detected features suggest the presence of allowed, disallowed, and resonant states. In EBER spectra of HEMT structures, peaks are apparent resulting from transitions between the valence band and the states in which the electrons are confined. We present examples of EBER determination of AlGaAs composition, single GaAs/AlGaAs quantum well evaluation, and HEMT characterization.

Growth and Characterization Of GexSi1−x/ Si Multiple Quantum Well Structures

1992 ◽  
Vol 263 ◽  
Author(s):  
D.W. Greve ◽  
R. Misra ◽  
M.A. Capano ◽  
T.E. Schlesinger
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Multiple Quantum Well ◽  
Small Variation ◽  
Multiple Quantum ◽  
X Ray Diffraction ◽  
High Quality ◽  
Quantum Well Structures ◽  
X Ray

ABSTRACTWe report on the growth and characterization of multiple quantum well structures by UHV/ CVD epitaxy. X- ray diffraction is used to verify the expected layer periodicity and to determine the quantum well thickness. Photoluminescence measurements show peaks which we associate with recombination of excitons in the quantum wells. The measurements are consistent with high quality layers with small variation in quantum well thickness across a wafer.

Characterization of GaAs/AlGaAs quantum wells and quantum wires by chemical lattice imaging

1994 ◽  
Vol 52 ◽  
pp. 736-737
Author(s):  
A. Carlsson ◽  
J.-O. Malm ◽  
A. Gustafsson
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Vapour Phase ◽  
Quantitative Information ◽  
Lattice Imaging ◽  
Vapour Phase Epitaxy ◽  
Metalorganic Vapour Phase Epitaxy ◽  
High Resolution Images

In this study a quantum well/quantum wire (QW/QWR) structure grown on a grating of V-grooves has been characterized by a technique related to chemical lattice imaging. This technique makes it possible to extract quantitative information from high resolution images.The QW/QWR structure was grown on a GaAs substrate patterned with a grating of V-grooves. The growth rate was approximately three monolayers per second without growth interruption at the interfaces. On this substrate a barrier of nominally Al0.35 Ga0.65 As was deposited to a thickness of approximately 300 nm using metalorganic vapour phase epitaxy . On top of the Al0.35Ga0.65As barrier a 3.5 nm GaAs quantum well was deposited and to conclude the structure an additional approximate 300 nm Al0.35Ga0.65 As was deposited. The GaAs QW deposited in this manner turns out to be significantly thicker at the bottom of the grooves giving a QWR running along the grooves. During the growth of the barriers an approximately 30 nm wide Ga-rich region is formed at the bottom of the grooves giving a Ga-rich stripe extending from the bottom of each groove to the surface.

A Possible Basis for Nondestructive Characterization of Ropes of Nylon 6

1997 ◽  
Vol 503 ◽  
Author(s):  
H. Jiang ◽  
M. K. Davis ◽  
R. K. Eby ◽  
P. Arsenovic
Keyword(s):  
Tensile Strength ◽  
Service Life ◽  
Fiber Diameter ◽  
Structural Parameters ◽  
Crystal Form ◽  
Nylon 6 ◽  
Remaining Service Life ◽  
Nondestructive Characterization ◽  
Fractional Content

ABSTRACTPhysical properties and structural parameters have been measured for ropes of nylon 6 as a function of the number of use operations. The fractional content of the α crystal form, sound velocity, birefringence, tensile strength and length all increase systematically and significantly with increasing the number of use operations. The fractional content of the γ crystal form and fiber diameter decrease with use. These trends indicate that the measurement of such properties and structural parameters, especially the length, provide a possible basis for establishing a reliable, rapid, and convenient nondestructive characterization method to predict the remaining service life of nylon 6 ropes.

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