Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosification

Zhu, Tongtong; Liu, Yingjun; Ding, Tao; Fu, Wai Yuen; Jarman, John; Ren, Christopher X.; Kumar, R. Vasant; Oliver, Rachel A.

doi:10.1038/srep45344

Cited by 59 publications

(60 citation statements)

References 42 publications

(49 reference statements)

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“…These properties combined present a unique opportunity to build GaN VCSELs. High-reflectance NP GaN DBR mirrors [117][118][119][120][121][122], optically pumped VCSELs [117,118], and resonant-cavity LEDs (RC-LEDs) [123,124] have been demonstrated by many groups in recently years. The ultimate viability of NP GaN DBRs will be determined by their long-term stability against thermal and electrical stresses.…”

Section: Nanoporous Gan/gan Dbrsmentioning

confidence: 99%

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: Nanoporous Gan/gan Dbrsmentioning

confidence: 99%

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

2019

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“…Thomas Swan close-coupled showerhead reactor and are situated in an etched micro-pillar structure containing porous DBRs (formed by electrochemical etching) for enhanced emission extraction efficiency. 35,36 Due to the modified droplet epitaxy growth of the QDs, they form as part of a fragmented quantum well. 32,37 Characterization of the QDs is performed optically using microphotoluminescence spectroscopy at a temperature of 7 K in a closed cycle cryostat under continuous wave (CW) laser excitation.…”

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confidence: 99%

Spectral diffusion time scales in InGaN/GaN quantum dots

Kang

Springbett

Zhu

et al. 2019

Applied Physics Letters

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A detailed temporal analysis of the spectral diffusion phenomenon in single photon emitting InGaN/GaN quantum dots (QDs) is performed via measurements of both time-varying emission spectra and single photon emission intensity autocorrelation times. Excitation dependent phenomena are investigated via the optical excitation of carriers into the GaN barrier material and also directly into InGaN. Excitation into InGaN reveals that the fastest environmental fluctuations occur on timescales as long as a few hundreds of nanoseconds: an order of magnitude longer than previously measured in GaN QDs. Such long time scales may in future allow for the generation of indistinguishable photons in spite of the fact that the experimentally measured linewidths are broad.

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“…The group at Yale reports a peak reflectance of >99.5% and stopband of 70 nm. An SEM image of a nanoporous DBR on c-plane with peak 70% porosity with ~30 nm pore size is shown in A single demonstration of a nanoporous DBRs using nonpolar a-plane GaN heteroepitaxially grown on r-plane sapphire has been reported by a group at the University of Cambridge [138]. Here, the EC etch was simplified by removing the fabrication steps and applying a one-step process.…”

Section: Discussionmentioning

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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Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosification

Cited by 59 publications

References 42 publications

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

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

Spectral diffusion time scales in InGaN/GaN quantum dots

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

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