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|Title:||Fabrication of quantum wire heterostructures and short wavelength photonic devices using the strain-induced lateral-layer ordering process|
|Author(s):||Chen, Arnold Chung-Ye|
|Doctoral Committee Chair(s):||Cheng, Keh-Yung|
|Department / Program:||Electrical Engineering|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Engineering, Electronics and Electrical
Engineering, Materials Science
|Abstract:||Research is currently underway on a variety of approaches to improve semiconductor laser performance. The use of quantum size effects has been studied for over 25 years. It has been predicted and shown that the incorporation of one-dimensionally confined quantum wells into laser devices can significantly improve their performance. The next logical step is to incorporate two-dimensionally confined quantum wire (QWR) structures into laser devices.
This thesis examines the in situ fabrication of QWRs, formed during molecular beam epitaxy growth, using the strain-induced lateral-layer ordering (SILO) process. The SILO process has many distinct advantages over other fabrication techniques: no pre-growth nor post-growth processing is necessary, no misoriented substrates are required, in situ growth prevents damage near QWR interfaces, high densities of quantum wires are formed, and high room temperature luminescence efficiency is achieved. It is also a versatile growth technique, which can be applied to many different material systems.
The SILO process creates a lateral composition modulation along the (110) direction, on a (001) substrate surface during the growth of short-period superlattices. It was found that this modulation is initiated from the microscopic strain on the surface during growth and that the modulated growth mode is stable once initiated. The induced lateral (110) composition modulation is large enough (20%) to produce a significant band gap discontinuity, while the modulation period is small enough (200 A) to induce quantum size effects. The combination of these effects produces lateral quantum wells (LQWs). Using the growth of GaInP LQWs, several different growth conditions were investigated. As expected, an increased substrate temperature produces a larger composition modulation. It was also determined that the LQWs always formed along the ($\bar 1$ 10) direction, primarily determined by the direction of the group-V dimer bonds on the surface during growth.
By coupling the one-dimensional confinement attainable from the LQWs, we are able to couple this with conventional quantum wells to obtain two-dimensionally confined structures. We utilize the SILO process for the growth of QWR heterostructures in the GaInP/GaAsP (6000 A), GaInP/GaAs (7000 A), GaInAsP/GaAs (1 $\mu$m), and GaInAs/InP (1.7 $\mu$m) material systems and provide evidence to assure two-dimensional confinement. We were able to accurately model the band structure for GaInP QWR heterostructures utilizing the model solid theory. By comparing the calculated transition energies to photoluminescence experiments, it was found that the triaxial strain variation inside the QWRs takes on a sinusoidal form along the (110) direction.
Finally, we demonstrate laser diode and light-emitting diode performance for visible spectrum QWR devices created using the SILO process. GaInP/GaAs laser diodes exhibited the anisotropic threshold current densities predicted from the QWR theory. At room temperature, devices exhibited threshold current densities of three times lower than in quantum well reference samples. Using the strain balance mechanism, short wavelength QWR light-emitting diodes, with emission near 6500 A(red), were fabricated on GaAsP substrates.
|Rights Information:||Copyright 1996 Chen, Arnold Chung-Ye|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9702474|
This item appears in the following Collection(s)
Dissertations and Theses - Electrical and Computer Engineering
Dissertations and Theses in Electrical and Computer Engineering
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois