Effect of the plasma etching on InAsP/InP quantum well structures measured through low temperature micro-photoluminescence and cathodoluminescence
Jean-Pierre LandesmanNebile Işık GöktaşRay LaPierreShahram Ghanad-TavakoliE. PargonCamille Petit‐EtienneChristophe LevalloisJose María JiménezShabnam Dadgostar
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Cathodoluminescence
Plasma Etching
InGaN/GaN quantum wells (QWs) grown with identical conditions on m-plane and c-plane GaN substrates were studied by cathodoluminescence spectroscopy. At a low current of 10 nA, the emission intensity and wavelength of the m-plane aligned QWs were found to be about two times stronger and 19.5 nm blueshifted with respect to that of the c-plane aligned QWs. An increase in the current over three orders of magnitude was found to result in an increase in the emission intensities, with faster saturation in the m-plane aligned QWs. This was explained by the screening of quantum-confined Stark effect in the emission efficiency of the c-plane aligned QWs.
Cathodoluminescence
Wide-bandgap semiconductor
Saturation (graph theory)
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Spatially resolved cathodoluminescence (CL) spectrum mapping revealed a strong exciton localization in InGaN single-quantum-wells (SQWs). Transmission electron micrographs exhibited a well-organized SQW structure having abrupt InGaN/GaN heterointerfaces. However, comparison between atomic force microscopy images for GaN-capped and uncapped SQWs indicated areas of InN-rich material, which are about 20 nm in lateral size. The CL images taken at the higher and lower energy side of the spatially integrated CL peak consisted of emissions from complementary real spaces, and the area was smaller than 60 nm in lateral size.
Cathodoluminescence
Wide-bandgap semiconductor
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Lateral variations of the exciton confinement energy Ecx have been investigated in a GaAs-AlGaAs multiple quantum well (MQW) structure using cathodoluminescence (CL) imaging in a scanning electron microscope. The MQW structure was grown by molecular beam epitaxy on a 2° misoriented GaAs substrate. The CL image of a defined MQW region does not change its lateral intensity distribution after removing different numbers of quantum wells by etching, indicating a correlated variation of Ecx between different quantum wells on a length scale of several μm. The variation of Ecx is connected to a mound like surface topography.
Cathodoluminescence
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The temperature dependence of the spectrally resolved cathodoluminescence intensity from a 3.5- nm-thick GaAs-AlGaAs single quantum well prepared by growth interrupted molecular beam epitaxy has been investigated between 5 and 120 K. As the temperature increases, we observe thermally activated carrier transfer from wider quantum well regions to narrower ones. This observation indicates that there is exciton localization within the wider quantum well regions, one or two monolayers larger in width, at low temperatures. The contrast in spectrally resolved cathodoluminescence images of the quantum well is significantly influenced by this exciton localization and therefore does not necessarily reflect the lateral island distribution.
Cathodoluminescence
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The gas plasma etching technique is investigated as a tool of etching micro-patterns ranged from a few microns to submicrons mainly with polycrystalline silicon films as materials to be etched. The gas plasma etching is verified to be the "nearly ideal" chemical etching. The undercutting at the top of the polycrystalline silicon film is nearly equal to the film thickness. It has been found that the etching in the diffused plasma is more suitable for etching micro-patterns and that the resist deformation is not observed after etching. The etching profile depends on the film thickness as well as on the applied RF power.
Plasma Etching
Dry etching
Polycrystalline silicon
Isotropic etching
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SEM-based cathodoluminescence (CL) is an important microcharacterization technique for the analysis of luminescent materials and defect-related effects. Cathodoluminescence (CL) imaging and spectroscopy have been used by the previous doctoral student, Lan-lin Chao, to investigate various properties of semiconductor materials, including GaAs/AlGaAs quantum well structures, ZnSe-based laser structures and GaN films. The present author has continued this work mainly on ZnCdSe quantum well structures fabricated by Prof. Tamargo's group at CUNY. The main concern for ZnCdSe quantum well (QW) luminescent devices is to understand how the as-grow defects or externally induced defects affect the performance of devices. Based on the CL studies of various samples, which are strained and latticematched, Cd-rich and poor, high and low in density of pre-existing defects, it is reported here that the degradation of ZnCdSe-based QW structures depends on the chemical composition of the QW layer. Associated with the difference of Cd composition x in QW layers Zn1-xCdxSe, the degradation has different morphologies. Cd-poor (x-0.2) QW structures usually form dark line defects (DLDs) along crystallographic directions after degradation, while Cd-rich (x-O.S) QW structures tend to form only dark spot defects (DSDs), independent of epitaxial strain and the density of as-grow defects. Besides the result from experiments (Chapter 4), some theoretical modeling calculations involved in CL studies are described in Chapter 3. They are (1) theoretical calculation of CL intensity and diffusion length of free carriers in quantum well structures, and (2) derivation of temperature-dependent population of free electron-hole pairs and excitons, which give theoretical support for conclusions drawn from our experiments. In the first two chapters, the background of this research, and cathodoluminescence and quantum well heterostructures is introduced.
Cathodoluminescence
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This paper reports research on deep etching of silicon carbide (SiC) to achieve isolated deep trenches in the same thick SiC substrates. This paper combines both plasma etching and electrochemical etching on p-type SiC above n-type SiC layers. Uniform and
Plasma Etching
Dry etching
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A two-step etching has been performed to eliminate the plasma charging damages during helicon-wave plasma metal etching without selectivity loss. This technique utilized a normal etching recipe to remove the Al film followed by an optimized etching recipe for the overetching step. By increasing the bias power and decreasing the source power, the optimum etching recipe can target the plasma more directionally and reduce the Al charging damages. Eventually, the damage mechanism was also reported.
Helicon
Plasma Etching
Dry etching
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The gas plasma etching technique is investigated as a tool of etching micro-patterns ranged from a few microns to submicrons mainly with polycrystalline silicon films as materials to be etched. The gas plasma etching is verified to be the ideal chemical etching. The undercutting at the top of the polycrystalline silicon film is nearly equal to the film thickness. It has been found that the etching in the diffused plasma is more suitable for etching micro-patterns and that the resist deformation is not observed after etching. The etching profile depends on the film thickness as well as on the applied RF power.
Plasma Etching
Dry etching
Polycrystalline silicon
Isotropic etching
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Citations (2)
The optical interferometry is a non-invasive plasma diagnostic method. Etch experiment were carried out in a high density plasma etching tool (ICP). The theoretical model for optical interferometric endpoint detection and prediction in plasma etching are presented. It is observed that the optical properties of oxide layer and polysilicon layer can affect the interferometric signals. The endpoint algorithm and real time plasma parameters diagnostics are discussed, then process control with optical interferometry during the poly-silicon etch is described. The endpoint prediction technique has been applied to poly-silicon gate etching in high density plasma etching tools.
Plasma Etching
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