Young-Dahl Jho

Gwangju Institute of Science and Technology

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Junichiro Kono

Rice University

Christopher J. Stanton

University of Florida

D. H. Reitze

University of Florida

H. Y. Hwang

University of Oxford

Ki‐Ju Yee

Chungnam National University

G. D. Sanders

University of Florida

C. J. Stanton

University of Florida

Hoon Jeong

Kwangwoon University

Dong‐Seon Lee

Gwangju Institute of Science and Technology

X. Wei

East China University of Science and Technology

Cooperative Institutions

Gwangju Institute of Science and Technology

Seoul National University

Government of the Republic of Korea

Korea Advanced Institute of Science and Technology

Korea Photonics Technology Institute

University of Florida

Korea Institute of Science and Technology

Pusan National University

Chungnam National University

Sungkyunkwan University

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Improved photoluminescence properties of selectively grown III-nitride core−shell nanorod array on quartz substrates

The Japan Society of Applied Physics (2018)

Si‐Young Bae Jung‐Wook Min Young-Dahl Jho Nobuyuki Ikarashi Hiroshi Amano

Nanorod

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Striking change of photoluminescence lifetime in biased InGaN quantum wells: effect of tunneling and piezoelectric field

APS (2001)

Young-Dahl Jho Eunsoon Oh D. S. Kim

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INTERBAND MAGNETO-SPECTROSCOPY OF A HIGH-DENSITY TWO-DIMENSIONAL ELECTRON GAS IN A STRONG IN-PLANE MAGNETIC FIELD

Young-Dahl Jho X. Wang F. V. Kyrychenko D. H. Reitze Christopher J. Stanton

Magneto

10.1142/9789812701923_0071

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Combined Effect of Carrier Localization and Polarity in InxGa1−xN/GaN Quantum Wells

Journal of Nanoscience and Nanotechnology (2014)

H. Y. Hwang Sang-Bae Choi Hoonill Jeong Dong‐Seon Lee Young-Dahl Jho

The influence of carrier localization and polarization-induced electric fields on the spectral variation of photoluminescence was comparatively studied in polar and semipolar InxGa1-x N/GaN strained quantum wells embedded in p-i-n diodes. Two representative structures with x = 0.16 for polar (0001) diodes and potential fluctuations for semipolar diodes grown along (1122) direction have been investigated with a reverse bias up to -4 V. From the s-shaped spectral shift as a function of temperature, the existence of single and triple localization traps was confirmed in polar and semipolar diodes. Within our bias range, we observed the monotonic blueshift with reverse bias in the polar sample, indicating that the carriers are laterally localized and thus influenced by the vertical piezoelectric fields. In clear contrast, the semipolar sample showed the blueshift of localized states only at low temperatures, while the deepest localization features were found at the highest available temperatures, overriding the influence of thermal activation and polarization fields.

Blueshift

Polarity (international relations)

10.1166/jnn.2015.10369

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Coherent phonons, nanoseismology and THz radiation in InGaN/GaN heterostructures

Superlattices and Microstructures (2003)

C. J. Stanton G. D. Sanders Raymond Liu Gia-Wei Chern Chi‐Kuang Sun

Photoexcitation

10.1016/j.spmi.2004.03.053

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Annealing-based manipulation of thermal phonon transport from light-emitting diodes to graphene

Journal of Applied Physics (2021)

Sang-Hyuk Park Hun Lee Sehyuk Lee Austin J. Minnich Woo‐Lim Jeong

We demonstrate that the thermal boundary conductivity (TBC) between graphene and GaN-based light-emitting diodes (LEDs) can be manipulated through thermal annealing, which is verified by measuring the acoustic phonons after reflection at the interface. Thermal annealing affects the interfacial morphology as evaluated by both the Raman spectra and the spatial profile of the graphene wrinkles in atomic force microscopy. By tracing the phase of ultrafast acoustic oscillations on the basis of the pump-probe scheme, we extract the phonon reflection coefficient at the interface as a function of annealing temperatures up to 400 °C. Specifically, the phase shift of transient phononic oscillations at the graphene/LED interface conveys the photoelastic response during the phonon transfer process and can be used for extracting the interfacial coupling rate, which is strongly enhanced around ≈200°C. By incorporating the heat capacity and the interfacial coupling constants into TBC, along with analytical modeling based on the phonon reflection coefficients, we show that the TBC increases with the minimized surface roughness of graphene side at 200 °C. This new comprehensive TBC extraction scheme could spark further discussion on improving the heat dissipation of LEDs.

Interfacial thermal resistance

10.1063/5.0069466

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Bias-Dependent Photoluminescence Analysis on InGaN/GaN MQW Solar Cells

한국진공학회 학술발표회초록집 (2013)

Jae‐Phil Shim Hoonil Jeong Sang-Bae Choi Young-Dahl Jho Young Ho Song

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<title>Femtosecond pump-probe and four-wave mixing studies of excitons in GaN</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2000)

Young-Dahl Jho Dai‐Sik Kim Arthur Fischer Jin‐Joo Song J. A. Kenrow

Femtosecond pump-probe (P-P) and four-wave mixing (FWM) experiments were performed simultaneously at 11 K on gallium nitride epilayers to study the initial temporal line-shapes of the exciton. A-B exciton beats were found in both P-P and FWM experiments near the exciton resonance. However, the differential reflection spectra showed a much slower rise time that persisted at longer negative time delay than the FWM signal or differential transition spectra at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including all Hartree Fock nonlinearities shows that this slow rise results from excitation induced dephasing, that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.

Dephasing

Four-wave mixing

10.1117/12.381469

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Superfluorescence from Magnetically Formed Quantum Dots: the Excitation Pulse-Width Dependence

Journal of the Optical Society of Korea (2008)

Young-Dahl Jho Jinho Lee G. D. Sanders Christopher J. Stanton D. H. Reitze

We investigated the laser pulse-width dependence of dense plasmas confined within the magnetic length of $In_{0.2}Ga_{0.8}As$/GaAs multiple quantum wells under high magnetic fields up to 31 T. To fully fill the Landau levels of effectively zero-dimensional system, we used intense femtosecond (fs) laser pulses to create carrier densities near $10^{13}/cm^2$. The observed photoluminescence showed a characteristic of superfluorescence, above critical magnetic field when being excited by pulses shorter than coherence buildup time.

10.3807/josk.2008.12.1.057

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Nexus between directionality of terahertz waves and structural parameters in groove patterned InAs

Journal of Applied Physics (2013)

Jong-Hyuk Yim Kyung-Gu Min Hoonil Jeong Eun Hye Lee Jin Dong Song

We have performed terahertz (THz)-time domain spectroscopy in various geometries, for characterizing the directivity of THz waves emitted from groove-patterned InAs structures. First, we have distinguished the THz emission mechanisms as a function of epilayer thickness. The carrier drift was predominant in thin sample group (10-70 nm) which the electronic diffusion motion was overriding the oppositely aligned drifting dipoles in thick sample group (370-900 nm) as revealed via amplitude and phase variations. By combined use of the electron-beam lithography and the inductively coupled plasma etching in 1 {\mu}m-thick InAs epilayers, we have further fabricated either asymmetric V-groove patterns or symmetric parabolic patterns. The THz amplitude was enhanced, particularly along line-of-sight transmissive direction when the groove patterns act as microscale reflective mirrors periodically separated by a scale of diffusion length.

Groove (engineering)

Microscale chemistry

10.1063/1.4795541

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Citations (5)