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The author discusses the story behind the invention of blue light-emitting diode .Topics include the progress made in combining white LED to blue LED using yellow phosphor, the material properties of indium gallium nitride as well as metal organic chemical vapor deposition as candidates for the development of blue LED and the future challenges of blue LED in the field of electronic. The author Shuji Nakamura, a Japanese physicist and the inventor of blue LED presents his autobiography.

Shuji Nakamura discovered p-type doping in Gallium Nitride (GaN) and developed blue, green, and white 'InGaN-based' light emitting diodes (LEDs) and blue laser diodes (LDs). His inventions made possible energy efficient, solid-state lighting systems and enabled the next generation of optical storage. In this biography, Shuji Nakamura tells the story of his personal life and his scientific career. [ABSTRACT FROM AUTHOR]

Investigations of the use of patterned porous GaN underlayers to achieve elastic relaxation of lattice‐mismatched top layers such as InGaN and AlGaN are reviewed. Thereby, the degree of relaxation of the top layers increases with the porosity and associated decrease in mechanical hardness of the porous GaN underlayers as well as with decreasing pattern size and increase in thickness of the lattice‐mismatched top layers, following the trends observed for nanostructures. Micrometer‐sized, high‐fill‐factor GaN‐on‐porous‐GaN tile arrays are used as universal substrate for the deposition of InGaN and AlGaN. Due to the elastic nature of the relaxation process, the threading dislocation density in the epitaxial material grown on top of the GaN‐on‐porous‐GaN tiles is equivalent to that in the GaN base material. InGaN and AlGaN layers grown on top of relaxed or partially relaxed InGaN or AlGaN underlayers by metal–organic chemical vapor deposition display a higher indium or aluminum content compared to their counterparts deposited on coloaded planar GaN reference wafers due to the decreased lattice mismatch. First applications of the patterned porous GaN‐based technology for optoelectronic and electronic devices are presented and serve as a pathway toward future implementations. [ABSTRACT FROM AUTHOR]

The finite element method was used to determine the thermal resistance of a flip-chip-bonded GaN-based vertical-cavity surface-emitting laser (VCSEL) with substrate removal and dielectric distributed Bragg reflectors (DBRs). In this work, we investigate the effects of the DBR configuration, mask layer alignment tolerances, aperture diameters, and cladding layer thicknesses on the thermal properties of the flip-chip design. The current flip-chip design suffers from high thermal resistance (∼4600 K W−1). By reducing the mask layer alignment tolerances and increasing the cladding thickness, the thermal resistance values could be made comparable to devices reported in the literature that achieved CW operation at room temperature (∼3000 K W−1). Low thermal resistance designs are critical to achieve CW operation and mitigate the effects of thermal roll-over in flip-chip GaN-based VCSELs. [ABSTRACT FROM AUTHOR]

By means of time-resolved emission spectroscopy, the emission dynamics of InGaN quantum well light-emitting devices is evaluated. The localization, radiation, and nonradiating recombination processes of the exciton are evaluated. It is found that there exist random potential fluctuations in the quantum well in samples with less than about 10% In in the InGaN activation layer. By means of these fluctuations, localization of the excitons can be attained. It is also found that the degree of localization increases as the In composition is increased, and that quantum dot-like regions are naturally formed in samples with an In content of more than about 20%. It is found that the capture of excitons by nonradiating recombination centers is suppressed and that a high-emission quantum efficiency is realized by such a pronounced localization. © 1998 Scripta Technica, Electron Comm Jpn Pt 2, 81(7): 45–56, 1998 [ABSTRACT FROM AUTHOR]

The effects of several design geometries on the thermal resistance for a flip‐chip GaN‐based VCSEL with dielectric distributed Bragg reflectors was studied by Mishkat‐Ul‐ Masabih (article no. 1600819) using finite‐element analysis. The current flip‐chip design suffers from high thermal resistance, preventing devices to lase under CW operation. It was found that including a patterned DBR with recessed metal, reducing the lithography alignment tolerances, and increasing the aperture size; all contributed to the reduction of the thermal resistance of the design. In addition, epitaxially increasing the cladding layer thickness on either side of the active region also lowered the thermal resistance significantly. The thermal resistance values for previously reported CW device configurations were also calculated and compared to our flip‐chip design. The internal temperature changes at the threshold were estimated for the devices, indicating why previous generations of our flip‐chip devices could not achieve CW lasing. Combining these techniques, the effects of thermal roll‐over can be mitigated; as the reduction of the device temperature is a key consideration for obtaining high output power CW GaN‐based VCSELs. [ABSTRACT FROM AUTHOR]