Fabrication of quantum wire heterostructures and short wavelength photonic devices using the strain-induced lateral-layer ordering process
Chen, Arnold Chung-Ye
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https://hdl.handle.net/2142/23474
Description
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
Issue Date
1996
Doctoral Committee Chair(s)
Cheng, Keh-Yung
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Engineering, Materials Science
Language
eng
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.
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