Dr. Ryoko Shimada Profile

Dr. Ryoko Shimada

at Japan Women's Univ

SPIE Involvement:

Author

Publications (8)

Proceedings Article | 12 March 2010 Paper

Internal quantum efficiency of m-plane InGaN on Si and GaN

J. Lee, X. Ni, M. Wu, X. Li, R. Shimada, Ü. Özgür, A. Baski, H. Morkoç, T. Paskova, G. Mulholland, K. Evans

Proceedings Volume 7602, 76021N (2010) https://doi.org/10.1117/12.843727

KEYWORDS: Light emitting diodes, Indium gallium nitride, Silicon, Gallium nitride, Sapphire, Polarization, Internal quantum efficiency, Quantum wells, Optical matrix switches, Optical components

Read Abstract +

Proceedings Article | 19 February 2009 Paper

GaN-based vertical cavities on highly reflective and crack-free nitride distributed Bragg reflectors

X. Ni, R. Shimada, T. Kang, J. Leach, Ü. Özgür, H. Morkoç

Proceedings Volume 7216, 72162F (2009) https://doi.org/10.1117/12.807902

KEYWORDS: Reflectivity, Gallium nitride, Semiconducting wafers, Distributed Bragg reflectors, Vertical cavity surface emitting lasers, Aluminum nitride, Silica, Scanning electron microscopy, Aluminum, Photomasks

Read Abstract +

Proceedings Article | 16 February 2009 Paper

Reduction of efficiency droop in InGaN-based blue LEDs

X. Ni, X. Li, J. Xie, Q. Fan, R. Shimada, Ü. Özgür, H. Morkoç

Proceedings Volume 7216, 72161W (2009) https://doi.org/10.1117/12.809877

KEYWORDS: External quantum efficiency, Light emitting diodes, Electroluminescence, Quantum efficiency, Indium gallium nitride, Quantum wells, Doping, Gallium, Blue light emitting diodes, Luminous efficiency

Read Abstract +

Proceedings Article | 12 February 2009 Paper

Effect of thermal annealing on Cu-related green luminescence in ZnO

V. Avrutin, M. Reshchikov, N. Izyumskaya, R. Shimada, S. Novak, H. Morkoç

Proceedings Volume 7217, 72170X (2009) https://doi.org/10.1117/12.809477

KEYWORDS: Zinc oxide, Annealing, Copper, Thermal effects, Excitons, Luminescence, Aluminum, Temperature metrology, Quantum efficiency, Zinc

Read Abstract +

Proceedings Article | 15 February 2008 Paper

Optical properties of polar, nonpolar, and semipolar InGaN/GaN multiple quantum wells on sapphire

X. Ni, R. Shimada, J. Leach, J. Xie, Ü. Özgür, H. Morkoç

Proceedings Volume 6894, 689428 (2008) https://doi.org/10.1117/12.763260

KEYWORDS: Gallium nitride, Quantum wells, Epitaxial lateral overgrowth, Polarization, Sapphire, Optical properties, Quantum efficiency, Metalorganic chemical vapor deposition, Luminescence, Scanning electron microscopy

Read Abstract +

The polarization fields in the c-axis-oriented hexagonal GaN system cause spatial separation of electrons and holes in quantum wells, reducing the quantum efficiency, and resulting in a red shift of the emission as well as a blue shift with increasing injected carrier density. In this paper, we report on the growth and optical characterization of InGaN/GaN multiple quantum wells (MQWs) on nonpolar (112¯0) a- and polar (0001) c-planes, as well as two semipolar planes, (112¯2) and (11¯01) of GaN. There are two kinds of a-plane used in this study. One of the (112¯0) a-planes was obtained on (11¯00) m-plane sapphire substrates during the epitaxial lateral overgrowth (ELO) of (112¯2) oriented semipolar GaN films, while the other one was planar a-plane GaN which was grown on (11¯01) r-plane sapphire substrates. The semipolar (112¯2) and (11¯01) planes were obtained as sidewall facets during the ELO of c-plane GaN with the mask stripes aligned along the GaN m-axis and a-axis, respectively. InGaN/GaN multiple quantum wells (MQWs) with a nominal well thickness of 4 nm and a barrier thickness of 8 nm were grown on these five GaN samples by metalorganic chemical vapor deposition. Excitation power dependent photoluminescence (PL) measurements were carried out on these quantum well structures to study the effect of polarization-induced electric field on the band-edge emission. The quantum-well emission energy from the two a-plane MQWs showed zero shift, compared to a 74 meV blue shift for the c-plane MQWs when the excitation power was increased from 1.3 mW to 37.0 mW. The semipolar (112¯2) showed a blue shift of 35 meV with increased excitation power, suggesting reduced polarization compared to that of c-plane. No quantum-well emission could be observed for the MQWs on (11¯01) semipolar planes. The shift in the quantum-well emission energy was attributed to the change of the screening effect of photon-generated carriers in the quantum wells at different excitation powers. For exact notation please see manuscript

Proceedings Article | 15 February 2008 Paper

ZnO hybrid microcavities grown by plasma assisted molecular beam epitaxy

Ryoko Shimada, Jinqiao Xie, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç

Proceedings Volume 6895, 68950I (2008) https://doi.org/10.1117/12.762299

KEYWORDS: Polaritons, Zinc oxide, Reflectivity, Excitons, Optical microcavities, Photons, Molecular beam epitaxy, Aluminum, Interfaces, Plasma

Read Abstract +

Proceedings Article | 15 February 2008 Paper

Effect of ion damage on optical properties of ZnO films grown by plasma-assisted MBE

V. Avrutin, M. Reshchikov, J. Nie, N. Izyumskaya, R. Shimada, Ü. Özgür, J. Foreman, H. Everitt, C. Litton, H. Morkoç

Proceedings Volume 6895, 68950Y (2008) https://doi.org/10.1117/12.764132

KEYWORDS: Ions, Zinc oxide, Sapphire, Plasma, Oxygen, Luminescence, Optical properties, Molecular beam epitaxy, Control systems, Excitons

Read Abstract +

Proceedings Article | 8 February 2007 Paper

High reflectivity ultraviolet distributed Bragg reflector based on AlGaN/AlGaN multilayer

Ryoko Shimada, Jinqiao Xie, Hadis Morkoç

Proceedings Volume 6473, 64731H (2007) https://doi.org/10.1117/12.707886

KEYWORDS: Gallium, Aluminum, Reflectivity, Aluminum nitride, Polaritons, Ultraviolet radiation, Gallium nitride, Distributed Bragg reflectors, Sapphire, Optical microcavities

Read Abstract +

Showing 5 of 8 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years