Design and Fabrication of Long -Wavelength Vertical -Cavity Surface -Emitting Lasers Using Wafer Bonding Technologies
Lin, Hung-Cheng
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/80780
Description
Title
Design and Fabrication of Long -Wavelength Vertical -Cavity Surface -Emitting Lasers Using Wafer Bonding Technologies
Author(s)
Lin, Hung-Cheng
Issue Date
2002
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
Language
eng
Abstract
Long-wavelength vertical-cavity surface-emitting lasers (VCSELs) emitting at 1.55 mum from GaInAsP/InP heterostructures are important optical sources for high-speed fiber-optic commutations. However, their development has been obstructed by the material disadvantages associated with the GaInAsP/InP distributed Bragg reflector (DBR) and the fabrication complexity of direct wafer bonding. In this work, a novel VCSEL fabrication method facilitated with new wafer bonding techniques has been developed to overcome these limitations. This process scheme provides more options on the DBR and substrate materials for long-wavelength VCSELs. In addition, the new wafer bonding techniques are less stringent on process requirements than the previous arts. Thus, the GaInAsP/InP VCSELs can be easily fabricated on lattice-mismatched substrates with high-contrast composite DBRs for a better performance, and therefore the need to grow thick epitaxial DBRs is eliminated. During the process development, substrate-independent DBRs such as polycrystalline-GaAs/Al-oxide, amorphous Si/Al-oxide, Si/Mg-oxide, and (Ga,As)/(Al,As) were investigated. New wafer bonding techniques using either spin-on glass or AuGeNiCr metal alloys as the bonding medium were developed. Using these wafer bonding techniques, the bonding interface can be formed outside the VCSEL cavity at low temperatures, reducing the mechanical and thermal impacts to the active region. In addition, processes for device formation such as ohmic contacts and chemical etching were studied and integrated. The results lead to the use of Si/Al-oxide DBRs and the metallic wafer bonding for the VCSEL fabrication. The Si/Al-oxide DBR provides a reflectance above 99.5% in six periods with a low thermal resistance and a broad stop bandwidth. The metallic wafer bonding offers a robust bonding interface, excellent thermal stability and optical reflectance. It also has a large process latitude and integration capability. Using the metallic bonding process, we successfully demonstrated 1.55 mum GaInAsP/lnP VCSELs on Si substrates. The fabricated VCSELs lase at 1.545 mum under pulsed operation at room temperature. The threshold current density is 1.2 kA/cm2 and the output power is 5 muW from a 30 mum x 30 mum device, which is limited by the heating of the resistive p-contact materials and the resulting offset of material gain. This process is useful to long-wavelength VCSELs and other applications.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
