Yasuhiko Matsushita

Fabrication of SiC Blue LEDs Using Off-Oriented Substrates

SiC blue LEDs were fabricated by the dipping technique, using 6H-SiC substrates whose (000)C face varied toward the [110] or [100] direction. The surface morphology of the epitaxial layers on the off-oriented substrates was a striped pattern perpendicular to the off-axis direction. By using off-oriented substrates, the degradation of SiC blue LEDs can be greatly reduced. High-efficiency blue LEDs (12 mcd at 20 mA) were fabricated by increasing the amount of Al dopant in the n-type layer.

Single Crystal Growth of 6H-SiC by a Vacuum Sublimation Method, and Blue LEDs

Undoped inch-sized n-type single crystal ingots of 6H-SiC have been successfully fabricated, and degradation (emission color shift from blue to greenish-blue) of SiC blue LEDs prepared using off-angle substrates is effectively prevented.

Dependence of SiC blue light-emitting diode efficiency on the p-type layer growth temperature

Dependence of SiC blue light-emitting diode (LED) efficiency on the p-type layer growth temperature in the liquid-phase epitaxial process was investigated. The external quantum efficiency of LEDs fabricated at a lower growth temperature was higher than that of those fabricated at a conventional growth temperature of 1720° C and maximized at a growth temperature of 1530° C. In this study, luminous intensity of 32 mcd was obtained at a forward current of 20 mA (λ P=467 nm).

High-brightness SiC blue LEDs and their application to full-color LED lamps.

炭化ケイ素 (SiC) を材料にして青色LEDの開発を進め, SiC結晶のオフアングル基板上にエピタキシャル層 (発光層) を形成する新しい結晶成長法を用いて高光度青色LED (樹脂モールド後, 光度12mcd) を開発した.さらに, この青色LEDとGaP赤, 緑色LEDを同一パッケージに組込み, 3原色光を光拡散剤で混色する方式を採用してフルカラーランプを試作した.各LEDの順方向電流値を独立に制御して, 赤, 緑, 青色の3原色, 合成中間および白色の各色光を同一ランプで初めて実現した.また, このフルカラーLEDを用いて, 絵素数が2×6のランプアレイを試作した.