Growth, Fabrication, and Characterization of Nonpolar III-Nitride Vertical-Cavity Surface-Emitting Lasers
- Author(s): Lee, Seunggeun
- Advisor(s): Denbaars, Steven P
- et al.
III-N vertical-cavity surface-emitting lasers (VCSELs) can be used for various applications including data communications, displays, optical sensors, and atomic clocks. However, III-N VCSELs have never been commercialized because of difficulties in fabrication, reliability, and high power lasing. From past few years, we have intensively developed VCSEL performance as well as reliability. We started to get milliwatt-class VCSELs under pulsed operation along with the maximum output power of 2.8 mW. This advancement could be achieved by applying new aperture design and developing overall processing steps. We also investigated thermal characteristics of VCSELs. Then, a VCSEL with a metalorganic chemical vapor deposition (MOCVD)-grown tunnel junction (TJ) contact and a buried tunnel junction (BTJ) VCSEL were demonstrated for the first time. Finally, the maximum output power of 726 µW under CW operation was achieved.
In the first chapter of this dissertation, motivations and applications of III-N VCSELs are presented along with introduction of VCSEL designs. In the second chapter, trials to optimize the VCSEL structure are demonstrated. Especially, the GaN TJ contact is intensely studied to replace a hybrid MOCVD/ molecular beam epitaxy (MBE) growth technique. Lastly, break down voltage of lightly doped p/n-GaN junction is verified for BTJ current aperture design. In the third chapter, processing steps are described for BTJ VCSELs and ion implant aperture (IIA) VCSELs. In the fourth chapter, optical and electrical characteristics of processed AII VCSELs and BTJ VCSELs are demonstrated and analyzed. Then, thermal analysis and effects were separately discussed. In the final chapter, conclusion and future works are mentioned.