Inductively coupled plasma (ICP) dry etching of metalorganic chemical vapor deposition-grown Ga-f... more Inductively coupled plasma (ICP) dry etching of metalorganic chemical vapor deposition-grown Ga-face and N-face GaN was performed under various etching conditions. Unlike wet etching, etch rates of the N-face GaN were close to those of the Ga-face GaN for most etching conditions. We also found that BCl3 and SF6 are not suitable for N-face etching, while conventional Cl2/Ar etching provides smoother N-face surfaces even at high etch rates. The dependence of the etch rate on the Cl2 fraction and the plasma condition suggested that adsorption of chlorine onto the GaN surface is the rate-limiting step of the etching at low chlorine coverage conditions, and ion bombardment is the rate-limiting step of the etching at high chlorine coverage conditions.
ABSTRACT Temperature-dependent carrier transport is investigated using ultrafast spectroscopy in ... more ABSTRACT Temperature-dependent carrier transport is investigated using ultrafast spectroscopy in a p-GaN/i-InGaN/n-GaN solar cell with heavily-doped layers to compensate for polarization charges at the heterointerface. We observe a flip in the transport direction at 110 K.
We report on pointed cone shaped blue light-emitting diodes (LEDs) based on ZnO and GaN wafer bon... more We report on pointed cone shaped blue light-emitting diodes (LEDs) based on ZnO and GaN wafer bonding. After wafer bonding of an n-type ZnO substrate to a III-nitride LED wafer, sapphire was removed and n- and p-pads were formed on the same side. Pointed hexagonal ZnO cone was formed by a selective chemical etching method. The output power and external
... a suspended geometry Natalie Fellows*, Hisashi Masui**, Hitoshi Sato, Hirokuni Asamizu, Micha... more ... a suspended geometry Natalie Fellows*, Hisashi Masui**, Hitoshi Sato, Hirokuni Asamizu, Michael Iza, Hong Zhong, Shuji Nakamura, and Steven P. DenBaars Materials Department, University of California at Santa Barbara, Santa Barbara CA, 93106, USA ...
Akihiko MURAI Ã, Daniel B. THOMPSON, Hirohiko HIRASAWA, Natalie FELLOWS, Stuart BRINKLEY, Choi Jo... more Akihiko MURAI Ã, Daniel B. THOMPSON, Hirohiko HIRASAWA, Natalie FELLOWS, Stuart BRINKLEY, Choi Joo WON, Michael IZA, Umesh K. MISHRA, Shuji NAKAMURA, and Steven P. DENBAARS Materials Department, Electrical and Computer Engineering Department, ...
High Brightness Violet InGaN/GaN Light Emitting Diodes on Semipolar ð10 1 1Þ Bulk GaN Substrates ... more High Brightness Violet InGaN/GaN Light Emitting Diodes on Semipolar ð10 1 1Þ Bulk GaN Substrates ... Anurag TYAGI 1Ã, Hong ZHONG 1, Natalie N. FELLOWS 1, Michael IZA 1, ... James S. SPECK 1,2, Steven P. DENBAARS 1,2, and Shuji NAKAMURA 1,2 ... 1Electrical and Computer ...
Abstract A first-moment analysis has been applied to electroluminescent spectra of polarized ligh... more Abstract A first-moment analysis has been applied to electroluminescent spectra of polarized light from InGaN/GaN light-emitting diodes prepared on (10\ bar {1}\ bar {1}) and (10\ bar {1}\ bar {3}) planes. The normalized first moment (the first moment divided by the zeroth ...
The authors report on InGaN microcavity light-emitting diodes with an effective thickness of at t... more The authors report on InGaN microcavity light-emitting diodes with an effective thickness of at the emission wavelength of . The starting material for the flip-chip laser lift-off device is a structure with an active region embedding six quantum wells, -thick AlGaN, and a GaN template ...
Limitations in extraction efficiency of gallium nitride ͑GaN͒ photonic crystal ͑PhC͒ light emitti... more Limitations in extraction efficiency of gallium nitride ͑GaN͒ photonic crystal ͑PhC͒ light emitting diodes ͑LEDs͒ are addressed by implementing an LED design using both two-dimensional PhCs in-plane and index guiding layers ͑IGLs͒ in the vertical direction. The effects of PhCs on light extraction and emission directionality from GaN LEDs are studied experimentally. Angular-resolved electroluminescence clearly shows the combined effect of controlling the vertical mode profile with the IGLs and tailoring the emission profile with the periodicity of the PhC lattice. Increases in directional emission as high as 3.5 times are achieved by taking advantage of this directionality and guided mode control.
An experimental method is demonstrated for the determination of internal quantum efficiency (IQE)... more An experimental method is demonstrated for the determination of internal quantum efficiency (IQE) in III-nitride-based light-emitting diodes (LEDs). LED devices surrounded with an optically absorbing material have been fabricated to limit collected light to photons emitted directly from the quantum wells across a known fraction of the recombination area. The emission pattern for this device configuration was modeled to estimate
Test structures were developed to experimentally measure the presence of electron overflow in lig... more Test structures were developed to experimentally measure the presence of electron overflow in light-emitting diodes (LEDs) under typical bias conditions. These test structures are comprised of a standard LED structure with an extra Mg-doped quantum well inserted on the p-type side of the electron blocking layer. Electrons escaping the active region recombine in the extra quantum well and the corresponding photon emission is observed. No electron overflow was observed at low current densities. At intermediate current densities where efficiency droop occurs, overflow was observed and increased with increasing current density. The onset of electron overflow occurred at slightly lower current densities than the onset of efficiency droop. Auger-assisted overflow, a by-product of the Auger process, is considered in addition to traditional overflow mechanisms.
Inductively coupled plasma (ICP) dry etching of metalorganic chemical vapor deposition-grown Ga-f... more Inductively coupled plasma (ICP) dry etching of metalorganic chemical vapor deposition-grown Ga-face and N-face GaN was performed under various etching conditions. Unlike wet etching, etch rates of the N-face GaN were close to those of the Ga-face GaN for most etching conditions. We also found that BCl3 and SF6 are not suitable for N-face etching, while conventional Cl2/Ar etching provides smoother N-face surfaces even at high etch rates. The dependence of the etch rate on the Cl2 fraction and the plasma condition suggested that adsorption of chlorine onto the GaN surface is the rate-limiting step of the etching at low chlorine coverage conditions, and ion bombardment is the rate-limiting step of the etching at high chlorine coverage conditions.
ABSTRACT Temperature-dependent carrier transport is investigated using ultrafast spectroscopy in ... more ABSTRACT Temperature-dependent carrier transport is investigated using ultrafast spectroscopy in a p-GaN/i-InGaN/n-GaN solar cell with heavily-doped layers to compensate for polarization charges at the heterointerface. We observe a flip in the transport direction at 110 K.
We report on pointed cone shaped blue light-emitting diodes (LEDs) based on ZnO and GaN wafer bon... more We report on pointed cone shaped blue light-emitting diodes (LEDs) based on ZnO and GaN wafer bonding. After wafer bonding of an n-type ZnO substrate to a III-nitride LED wafer, sapphire was removed and n- and p-pads were formed on the same side. Pointed hexagonal ZnO cone was formed by a selective chemical etching method. The output power and external
... a suspended geometry Natalie Fellows*, Hisashi Masui**, Hitoshi Sato, Hirokuni Asamizu, Micha... more ... a suspended geometry Natalie Fellows*, Hisashi Masui**, Hitoshi Sato, Hirokuni Asamizu, Michael Iza, Hong Zhong, Shuji Nakamura, and Steven P. DenBaars Materials Department, University of California at Santa Barbara, Santa Barbara CA, 93106, USA ...
Akihiko MURAI Ã, Daniel B. THOMPSON, Hirohiko HIRASAWA, Natalie FELLOWS, Stuart BRINKLEY, Choi Jo... more Akihiko MURAI Ã, Daniel B. THOMPSON, Hirohiko HIRASAWA, Natalie FELLOWS, Stuart BRINKLEY, Choi Joo WON, Michael IZA, Umesh K. MISHRA, Shuji NAKAMURA, and Steven P. DENBAARS Materials Department, Electrical and Computer Engineering Department, ...
High Brightness Violet InGaN/GaN Light Emitting Diodes on Semipolar ð10 1 1Þ Bulk GaN Substrates ... more High Brightness Violet InGaN/GaN Light Emitting Diodes on Semipolar ð10 1 1Þ Bulk GaN Substrates ... Anurag TYAGI 1Ã, Hong ZHONG 1, Natalie N. FELLOWS 1, Michael IZA 1, ... James S. SPECK 1,2, Steven P. DENBAARS 1,2, and Shuji NAKAMURA 1,2 ... 1Electrical and Computer ...
Abstract A first-moment analysis has been applied to electroluminescent spectra of polarized ligh... more Abstract A first-moment analysis has been applied to electroluminescent spectra of polarized light from InGaN/GaN light-emitting diodes prepared on (10\ bar {1}\ bar {1}) and (10\ bar {1}\ bar {3}) planes. The normalized first moment (the first moment divided by the zeroth ...
The authors report on InGaN microcavity light-emitting diodes with an effective thickness of at t... more The authors report on InGaN microcavity light-emitting diodes with an effective thickness of at the emission wavelength of . The starting material for the flip-chip laser lift-off device is a structure with an active region embedding six quantum wells, -thick AlGaN, and a GaN template ...
Limitations in extraction efficiency of gallium nitride ͑GaN͒ photonic crystal ͑PhC͒ light emitti... more Limitations in extraction efficiency of gallium nitride ͑GaN͒ photonic crystal ͑PhC͒ light emitting diodes ͑LEDs͒ are addressed by implementing an LED design using both two-dimensional PhCs in-plane and index guiding layers ͑IGLs͒ in the vertical direction. The effects of PhCs on light extraction and emission directionality from GaN LEDs are studied experimentally. Angular-resolved electroluminescence clearly shows the combined effect of controlling the vertical mode profile with the IGLs and tailoring the emission profile with the periodicity of the PhC lattice. Increases in directional emission as high as 3.5 times are achieved by taking advantage of this directionality and guided mode control.
An experimental method is demonstrated for the determination of internal quantum efficiency (IQE)... more An experimental method is demonstrated for the determination of internal quantum efficiency (IQE) in III-nitride-based light-emitting diodes (LEDs). LED devices surrounded with an optically absorbing material have been fabricated to limit collected light to photons emitted directly from the quantum wells across a known fraction of the recombination area. The emission pattern for this device configuration was modeled to estimate
Test structures were developed to experimentally measure the presence of electron overflow in lig... more Test structures were developed to experimentally measure the presence of electron overflow in light-emitting diodes (LEDs) under typical bias conditions. These test structures are comprised of a standard LED structure with an extra Mg-doped quantum well inserted on the p-type side of the electron blocking layer. Electrons escaping the active region recombine in the extra quantum well and the corresponding photon emission is observed. No electron overflow was observed at low current densities. At intermediate current densities where efficiency droop occurs, overflow was observed and increased with increasing current density. The onset of electron overflow occurred at slightly lower current densities than the onset of efficiency droop. Auger-assisted overflow, a by-product of the Auger process, is considered in addition to traditional overflow mechanisms.
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Papers by Michael Iza