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Featured researches published by Maki Sugai.


Proceedings of SPIE | 2012

Effect of dislocation density on efficiency curves in InGaN/GaN multiple quantum well light-emitting diodes

Yoshiyuki Harada; Toshiki Hikosaka; Shigeya Kimura; Maki Sugai; Hajime Nago; Koichi Tachibana; Naoharu Sugiyama; Shinya Nunoue

The contribution of reduction of threading dislocation densities (TDDs) to optical properties is investigated for InGaN/GaN light-emitting diodes (LEDs) grown on sapphire substrate. The external quantum efficiency (EQE) curves depending on the TDDs are discussed both theoretically and experimentally. At the current density of <20 A/cm2, the EQE increases with decreasing the edge-type TDD from 5 e8/cm2 to 2 e8/cm2. The current density at the maximum EQE shifts to lower value as the edge-type TDD decreases, whereas the EQE presents no remarkable difference in the highercurrent density range irrespective of the TDD. According to the rate equation (ABC) model, the peak shift reflects the Shockley-Read-Hall non-radiative process (A coefficient). Analysis of the photoluminescence (PL) decay and the dependence of integrated PL intensity on excitation power reveals that the threading dislocations act as non-radiative recombination centers in the multiple quantum well active region. The TDD of <2 e8/cm2 is required for highly efficient blue LEDs operating at current density of around 15 A/cm2, whereas the TDD of <5 e8/cm2 in required for the LEDs operating at around 50 A/cm2.


international semiconductor laser conference | 2008

High-efficiency GaN-based laser diodes for solid-state lighting

Shinji Saito; Yasushi Hattori; Maki Sugai; Yoshiyuki Harada; H. Jongil; Shinya Nunoue

GaN-based laser diodes (LDs) with a slope efficiency of 2.6 W/A are presented. The white light source was fabricated by using 405 nm LDs and phosphors. The luminous flux was estimated to be 200 lm.


Archive | 2005

LIGHT-EMITTING DEVICE AND ILLUMINATING DEVICE

Takahiro Sato; Shinji Saito; Shinya Nunoue; Yasushi Hattori; Maki Sugai


Archive | 2014

Semiconductor light emitting device, nitride semiconductor layer growth substrate, and nitride semiconductor wafer

Toshiki Hikosaka; Yoshiyuki Harada; Maki Sugai; Shinya Nunoue


Archive | 2012

SEMICONDUCTOR LIGHT EMITTING DEVICE, NITRIDE SEMICONDUCTOR LAYER, AND METHOD FOR FORMING NITRIDE SEMICONDUCTOR LAYER

Toshiki Hikosaka; Yoshiyuki Harada; Maki Sugai; Shinya Nunoue


Archive | 2012

NITRIDE SEMICONDUCTOR DEVICE AND NITRIDE SEMICONDUCTOR LAYER GROWTH SUBSTRATE

Koichi Tachibana; Hisashi Yoshida; Hiroshi Ono; Hajime Nago; Yoshiyuki Harada; Toshiki Hikosaka; Maki Sugai; Toshiyuki Oka; Shinya Nunoue


Archive | 2011

Nitride semiconductor device and substrate for growing nitride semiconductor layer

Koichi Tachibana; 浩一 橘; Gakushi Yoshida; 学史 吉田; Hiroshi Ono; 浩 大野; Hajime Nago; 肇 名古; Yoshiyuki Harada; 佳幸 原田; Toshiteru Hikosaka; 年輝 彦坂; Maki Sugai; 麻希 菅井; Toshiyuki Oka; 俊行 岡; Shinya Nunoue; 真也 布上


Archive | 2015

Semiconductor light emitting device with an aluminum containing layer formed thereon

Jongil Hwang; Shinji Saito; Maki Sugai; Rei Hashimoto; Yasushi Hattori; Masaki Tohyama; Shinya Nunoue


Archive | 2012

Lichtemittierendes Halbleiterbauelement, Nitrid-Halbleiterschicht und Verfahren zur Herstellung einer Nitrid-Halbleiterschicht

Toshiki Hikosaka; Yoshiyuki Harada; Maki Sugai; Shinya Nunoue


Archive | 2008

Dispositif luminescent à semiconducteur

Yasushi Hattori; Shinji Saito; Shinya Nunoue; Eiji Muramoto; Koichi Tachibana; Saori Abe; J. I. Hwang; Maki Sugai

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