Y.S. Tang
University of Glasgow
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Featured researches published by Y.S. Tang.
Journal of Applied Physics | 1991
Y.S. Tang
Photoreflectance line shapes of various semiconductor microstructures were discussed in this paper. Formulas suitable for application in low‐dimensional structures were given and used to analyze experimental results from various semiconductor microstructures including GaAs nipi structures, GaAs/AlGaAs multiple quantum wells, InGaAs/GaAs strained‐layer superlattices, and
Journal of Electronic Materials | 1995
Y.S. Tang; C. M. Sotomayor Torres; R. A. Kubiak; T.E. Whall; E. H. C. Parker; H. Presting; Horst Kibbel
Nanometer-scale quantum dots based on a series of Si/Si0.91Ge0.09 strained layer superlattices and a Si9/Ge6 strain-symmetrized superlattice were fabricated using electron beam lithography and reactive ion etching. They were investigated by photoluminescence and photoreflectance. It was found for the first time that the quantum efficiency of optical emission from the quantum well layers increased by over two orders of magnitude when the quantum dot sizes were reduced to ≤100 nm.
Solid State Communications | 1995
Y.S. Tang; C. M. Sotomayor Torres; B. Dietrich; W. Kissinger; T.E. Whall; E. H. C. Parker
Abstract SiSi 1−x Ge x (x=0.2∼0.3) quantum dots of 50∼60nm in diameter fabricated by using electron beam lithography and reactive ion etching were characterized by Raman spectroscopy. Clear evidence of process-induced strain relief was found in addition to the observation of features from enhanced multi-phonons and SiSi 1−x Ge x intermixing arising from the process-induced crystal symmetry breakdown in the nanostructured quantum dots.
Applied Physics Letters | 1994
H. Qiang; Fred H. Pollak; Y.S. Tang; P. D. Wang; C. M. Sotomayor Torres
Using contactless photoreflectance at 300 K, we have studied several GaAs/Ga0.7Al0.3As quantum dot arrays fabricated by reactive‐ion etching using SiCl4. The spectrum from a control sample that had no dots also was recorded. From the observed shifts of the fundamental conduction to heavyand of the process‐induced strain in the dots.
Applied Physics Letters | 1991
Xiaodan Pan; David R. Allee; A. N. Broers; Y.S. Tang; C. W. Wilkinson
Because of its unique properties and well‐established processing techniques, SiO2 has wide application in the integrated circuit industry. The ability to directly pattern SiO2 with nanometer resolution by electron beam irradiation is therefore of great importance in the fabrication of both ultrasmall conventional and quantum devices. In this letter we demonstrate the replication of trenches with feature sizes as small as 10 nm into polycrystalline silicon and single‐crystal and via reactive ion etching by using electron beam direct patterned SiO2 as the mask.
Journal of Applied Physics | 1998
Boon S. Ooi; Y.S. Tang; A. Saher Helmy; A.C. Bryce; J.H. Marsh; M. Paquette; Jacques Beauvais
We report the fabrication of GaAs/AlGaAs quantum well wires using implantation of As at 45 keV to induce quantum well intermixing. The intermixing process was first characterized giving optimized annealing parameters of 875 °C for 30 s and an implantation dose of 1×1013 cm−2. Wire widths from 35 to 1000 nm were defined using e-beam lithography followed by lift-off. Photoluminescence spectra from the lateral wells and barriers were observed from samples with wires as narrow as 50 nm. The energies of the lateral wells were found to remain constant for wire widths between 1000 and 150 nm, and start to shift significantly towards high energy for 80 nm wires, the signal from the lateral well eventually merging with that from the lateral barrier for 35 nm wires. An intermixing radius of about 17 nm was estimated for the process. Photoreflectance measurements were also carried out on these wire samples, showing that the wires appear to have a parabolic lateral potential and clear interwire coupling was observed ...
Applied Physics Letters | 1991
Y.S. Tang; C. D. W. Wilkinson
Reactive ion etching of polycrystalline silicon using SiCl4 was used to etch 70‐nm‐wide structures. The etching mechanism of the process was investigated by using emission spectroscopy. It was found that the principal etchant for polycrystalline silicon is Cl+2.
Journal of Materials Science: Materials in Electronics | 1995
Y.S. Tang; C. M. Sotomayor Torres; Terry E. Whall; E. H. C. Parker; H. Presting; Horst Kibbel
This paper reviews the current research status on the optical properties of Si-Si1−xGex and Si-Ge nanostructures. Although this is a relatively new field, existing research has already achieved promising results in terms of both physics and possible device applications including the effect of process-induced strain in nanostructures, quantum confinement and improved optical efficiency of collective excitation in wires with reduced dimension, and especially the huge improvement of optical efficiency in quantum dots after nanofabrication. These results potentially open a new field of research into both the physics of Si-Si1−xGex nanostructures and the possible applications of them in cheap Si based optoelectronic industry.
Journal of Electronic Materials | 1996
Y.S. Tang; C. M. Sotomayor Torres; S. Nilsson; B. Dietrich; W. Kissinger; Terry E. Whall; E. H. C. Parker; W. X. Ni; G. V. Hansson; H. Presting; Horst Kibbel
Quantum dots of 50 ~ 60 nm diameter fabricated from both Si/Si1-xGex (x = 0.1 ~ 0.3) strained layer superlattices and a strain symmetried Si9/Ge6 superlattice were investigated by a combination of Raman scattering, photoluminescence, and electroluminescence spectroscopy. It was found that, in addition to an enhanced luminescence intensity of the dots by over two orders of magnitude and improved luminescence quenching temperature, all of the nanostructure dots have residual built-in elastic strains, which are of the order of ~50% of the values in corresponding pseudomorphic heterostructures. This result suggests a possible mechanism for explaining the huge enhancement of the optical efficiency in our luminescence measurements.
Journal of Applied Physics | 1995
Y.S. Tang; P. D. Wang; C. M. Sotomayor Torres; B. Lunn; D. E. Ashenford
This article reports a photoreflectance study of the process‐induced strains in both dry etched CdTe/Cd0.875Mn0.125Te and GaAs/Al0.3Ga0.7As nanostructures patterned by electron beam lithography. The results show that compressive strains can be introduced in both the dry etched nanostructures and the layers underneath the etched surfaces due to the introduction of defect complexes and/or crystographic damage inflicted in the fabrication process. The effect of post dry etch thermal annealing on the strains in the dry etched nanostructures has also been studied.