Fabrication of LED Based on III-V Nitride and its Applications
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Fabrication of Applications
LED
Based
on
III-V
E1.6.1
Nitride
and
Naoki Shibata O p t e l e c t r o n i c s Te c h n i c a l d i v. , To y o d a G o s e i C o . , Lt d . , 710 Origuchi Shimomiyake heiwa-cho Nakashima-gun 490-1312, Japan
its
Aichi
ABSTRACT Short wavelength LED (TG Purple) based on III-V nitride semiconductors is established in addition to blue and green. This short wavelength LED is realized b y adjusting “Indium” c h e mi c a l c on t e n t o f t h e we l l l a ye r. Li g h t o u t p u t p o w e r o f “ T G P u r p l e ” i s h i g h a n d F W H M i s n a r r o w. “ T G P u r p l e ” i s a p p l i e d t o light source of white LED. Combination of “TG Purple” and various phosphors can generate white light with high luminous intensity and good color rendering. “TG Purple” is also a p p l i ed t o l i gh t s ou r c e o f a i r-p u ri f i e r. T h i s a i r- p u r i fi e r wa s equipped in a car and several applications of this system are widely utilized in room air conditioners and refrigerators. INTRODUCTION The LED (Light Emitting Diodes) has the features of low e n e r g y c o n s u m p t i o n , h i g h l u m i n o s i t y, a n d l o n g l i f e t i m e w h e n compared with the conventional incandescent lamp. Therefore, the development of LED with higher efficiency and higher luminosity is still expected. The color (wavelength) of LED is determined by the bandgap energy of the semiconductor material used for LED. The bandgap energy is peculiar characteristic of the semiconductor materials. Therefore, the development of LED means the development of the semiconductor material itself. The III-V nitride semiconductors had been expected to be suitable for LED with colors covering ultraviolet, blue through green, and to be suitable for the laser diode (LD) with short wavelength because of the wide bandgap energy and the direct transition band structure. Although the III-V nitride semiconductors had not been applied to the commercial devices due to its low crystal qualities, the following breakthrough technologies enabled III-V nitride to be used for the device having high quality semiconductor layers. The introduction of an AlN buffer layer on sapphire
E1.6.2
substrate made it possible to obtain high crystal quality of the III-V nitride semiconductors, especially GaN, with a smooth surface by metal organic chemical vapor deposition (MOCVD)[1]. The N-type conduction was realized by controlling the electron carrier concentration using the Si doping technology to GaN [2][3] for the first time. On the other hand, P-type conduction of GaN was established by Mg doping and low electron energy beam irradiation technology (LEEBI)[4]. We s t a r t e d t h e j o i n t r e s e a r c h p r o j e c t w i t h P r o f . A k a s a k i in 1986, and JCI entrusted us to develop blue LED under the s u p e r v i s i o n o f P r o f . A k a s a k i . We s u c c e e d e d i n t h e d e v e l o p m e n t of the brightest blue LED in 1991[5]. This is the Zn doping type of GaN based LEDs. The intensity of this LED wa
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