Lateral optical confinement of GaN-based VCSEL using an atomically smooth monolithic curved mirror

Hamaguchi, Tatsushi; Tanaka, Masayuki; Mitomo, Jugo; Nakajima, Hiroshi; Ito, Masamichi; Ohara, Maho; Kobayashi, Noriko; Fujii, Kentaro; Watanabe, H.; Satou, Susumu; Koda, Rintaro; Narui, Hironobu

doi:10.1038/s41598-018-28418-6

Cited by 60 publications

(81 citation statements)

References 21 publications

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“…Given the difficulty presented in 4.1 and 4.2 in forming all dielectric mirrors, Sony recently demonstrated yet another version of VCSEL with dielectric mirrors [93] using the concept of "external cavity" where a curved dielectric mirror is coated on the substrate side after substrate thinning [94][95][96]. This implementation, sometimes called thin-disk laser, is possibly the least complicated in terms of both epitaxial growth and device fabrication compared to all other approaches ( Figure 10).…”

Section: Non-epitaxial Dbrs Through Substrate Thinning and Curved Diementioning

confidence: 99%

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Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers

2019

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A distributed Bragg reflector (DBR) is a key building block in the formation of semiconductor microcavities and vertical cavity surface emitting lasers (VCSELs). The success in epitaxial GaAs DBR mirrors paved the way for the ubiquitous deployment of III-V VCSELs in communication and mobile applications. However, a similar development of GaN-based blue VCSELs has been hindered by challenges in preparing DBRs that are mass producible. In this article, we provide a review of the history and current status of forming DBRs for GaN VCSELs. In general, the preparation of DBRs requires an optimization of epitaxy/fabrication processes, together with trading off parameters in optical, electrical, and thermal properties. The effort of epitaxial DBRs commenced in the 1990s and has evolved from using AlGaN, AlN, to using lattice-matched AlInN with GaN for DBRs. In parallel, dielectric DBRs have been studied since 2000 and have gone through a few design variations including epitaxial lateral overgrowth (ELO) and vertical external cavity surface emitting lasers (VECSEL). A recent trend is the use of selective etching to incorporate airgap or nanoporous GaN as low-index media in an epitaxial GaN DBR structure. The nanoporous GaN DBR represents an offshoot from the traditional epitaxial approach and may provide the needed flexibility in forming manufacturable GaN VCSELs. The trade-offs and limitations of each approach are also presented.

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Section: Non-epitaxial Dbrs Through Substrate Thinning and Curved Diementioning

confidence: 99%

“…(b) Laser scanning confocal microscope images of lenslets (diameter = 55 μm) fabricated on the (000-1) plane of GaN wafer. (c) Cross-sectional TEM image of the curved mirror of the device used for an optical pumping test [93]. Copyright 2018 Scientific Reports.…”

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confidence: 99%

Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers

2019

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“…The filamentary nature of the emission across the aperture is commonly observed in IIInitride VCSELs, but its origin is not well understood [78,80,81]. Previous reports have implicated poor transverse optical confinement, inhomogeneous current spreading of the ITO, and/or localized variations of the contact resistance despite having uniform layer refractive indices inside the cavity [92,190]. (a).…”

Section: Optoelectronic Characteristicsmentioning

confidence: 99%

“…In general, increasing the effective index contrast between the core and the cladding regions will tightly confine the mode inside the core, allowing higher order modes to be easily supported in the VCSEL [69,83]. But a large abrupt change in ∆ can also result in increase scattering and diffraction losses in the cavity, so typically ∆ / is maintained below 2% [69,92,205].…”

Section: Optoelectronic Characteristicsmentioning

confidence: 99%

Nonpolar GaN-based VCSELs with lattice-matched nanoporous distributed Bragg reflector mirrors

Mishkat-Ul-Masabih

Aragon

Monavarian

et al. 2020

Gallium Nitride Materials and Devices XV

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I am grateful to many people for making this work possible. First and foremost, I would like to thank my advisor Prof. Daniel Feezell for his dedicated guidance and support. Early on in my degree, I remember him mentioning that VCSEL projects are always of high risk and high reward. For the longest time, I doubted myself on whether I would be able to fulfill all the project requirements. But, Prof. Feezell believed in my ability and urged me to push forward which ultimately lead to groundbreaking results from my VCSEL project. Not only did I learn a ton from his vast knowledge on IIInitride materials and devices, his constructive criticisms greatly improved the quality of my work and allowed me to grow as a researcher. Next, I am thankful to my committee members and collaborators, Prof. Ganesh Balakrishnan, Prof. Sang Han, and Dr. Ting Luk for their time and suggestions. Their valuable insight on optical, electrical, and mechanical properties of semiconductors helped me tremendously in understanding the material characteristics and device performance of my VCSELs. I cannot express the immense gratitude I feel for my fellow group members, both past and present. All of whom have helped me towards the completion of my PhD in some way or another. Many thanks to Ashwin, Morteza, Mohsen, and Mike for introducing me to MOCVD and for taking care of my growths when I was busy doing something else. Discussions regarding fabrication with Andrew, Mahmoud, Rhett, Kenny, Farnood, and Abdel have always helped me in developing processes very v quickly and reliably. I am also grateful to Serdal, Arman, and Isaac for assisting me in various material and device related characterizations. Many of the accomplishments mentioned in this thesis could not have been possible without the support of the technical and/or administrative staff. As such, I am forever indebted to the ECE, CHTM, and CINT staff members for putting up with my numerous requests and questions throughout the years. Beyond the appreciation of the technical side of things, I would like to thank all my friends from back home and the ones I made during the course of my study. They were always there to lend a helping hand or to simply distract me from work whenever graduate student life became too overwhelming. Furthermore, I must also acknowledge the Bangladeshi community here at UNM for making Albuquerque feel like home, even though my real home is halfway around the world. Looking back, I will forever cherish these memories. Last, but certainly not least, I would like to thank my parents, my older sister, and my younger brother. I would not be where I am at today without their unconditional love and encouragement. They have sacrificed a lot so that I can pursue a career of my choice, even if it meant me being away from home for an extended period time. I only hope that the work I performed in this thesis is substantial enough to repay them and make them proud. vi

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“…In general, the indium tin oxide (ITO) has been the most commonly used material to improve lateral current spreading on the p-side of the VCSEL device. However, the high absorption loss of ITO can lead to significantly higher threshold currents and lower light outputs [17,18]. In this work, the numerical simulation was performed via Crosslight software Photonic Integrated Circuit Simulator in 3D (PICS3D) on tunnel junction (TJ) structure GaN VCSELs [19][20][21] as well as an ITO based VCSEL which we had used before [16].…”

Section: Introductionmentioning

confidence: 99%

Design and Fabrication of the Reliable GaN Based Vertical-Cavity Surface-Emitting Laser via Tunnel Junction

Shen

Yeh

et al. 2019

Crystals

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In this study, we theoretically designed and experimentally fabricated an InGaN vertical-cavity surface-emitting laser (VCSEL) with a tunnel junction (TJ) structure. From numerical simulation results, the optical loss of the device can be reduced by a TJ structure. Additionally, the leakage current of the VCSEL with TJ structure was much smaller than that of the VCSEL with an Indium-Tin-Oxide (ITO) layer. We have been demonstrated that laser output performance is improved by using the TJ structure when compared to the typical VCSEL structure of the ITO layer. The output power obtained at 2.1 mW was enhanced by a factor of 3.5 by the successful reduction of threshold current density (Jth) from 12 to 8.5 kA/cm2, and the enlarged slope efficiency was due to less absorption in VCSEL with a TJ structure. Finally, the samples passed the high temperature (70 °C) and high operation current (1.5 × Jth) test for over 500 h.

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Lateral optical confinement of GaN-based VCSEL using an atomically smooth monolithic curved mirror

Cited by 60 publications

References 21 publications

Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers

Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers

Nonpolar GaN-based VCSELs with lattice-matched nanoporous distributed Bragg reflector mirrors

Design and Fabrication of the Reliable GaN Based Vertical-Cavity Surface-Emitting Laser via Tunnel Junction

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