Blue LED
Refers to the blue light-emitting diodes. The center of the emission wavelength is around 470nm. For lighting fixtures and indicators shown in blue part of the light source, the blue light of LED display and LCD panel back-illuminated light source. With the phosphor material combinations available to white light. White LEDs generally use a combination of the structure of the blue LED and the fluorescent material.
Blue led driver 120w can be widely used the opportunity, Nichia Chemical Industries in December 1993, the first time in the industry, developed a light intensity of 1cd above varieties. Prior to this, there is no blue high purity and has a strong practical light LED. Therefore, the large-size display with LED can not achieve full-color display.
The material of the blue LED using gallium nitride (GaN) semiconductor class. Was prevalent before the blue LED of zinc selenide (ZnSe), semiconductor development, since the GaN semiconductor December 1993 high brightness blue LED was developed mainstream of the blue LED using GaN
The blue LED structure on the surface of the sapphire or SiC and base, the semiconductor layer of overlapping laminated aluminum nitride (AlN) and GaN semiconductor layer. Called active layer, the luminous blue part of the set of p-type GaN semiconductor layer and the n-type GaN semiconductor layer overlapping structure.
The pn junction is the structure must be used by the production of high brightness LED. In red and other use of materials other than GaN LED, pn junction long before mainstream construct. Before the 1993 high-brightness blue LED Flood light 10W available, the use of GaN materials is difficult to achieve the pn junction. The reason is made of n-type GaN semiconductor layer is relatively simple, but the production of p-type GaN semiconductor layer is more difficult. GaN type semiconductor layer between the p-type GaN semiconductor layer and the n-type GaN-type semiconductor layer configuration using multiple quantum well structure, and to further improve the quality of the GaN type semiconductor layer, light strong to obtain a substantial increase.
Green LED
Launch green diode. Luminescence center wavelength at about 560nm. For the neon lights and indicator light of the LED display and LCD panel, the backlight light source.
The green LED and red LED and blue LED, that there are still large room for improvement. Modulated into a high brightness and balanced white of a combination of red LEDs, green LEDs and blue LEDs LED display or LCD panel, the backlight light source, in order to take into account human visual sensitivity, the allocation ratio of the RGB three-color LED light needs about 3:6:1 or about 3:7:1. Due to insufficient brightness of the green LED, so you must use more than one green LED Floodlight 80W to increase the output power. Green LED is mainly used in GaN-type semiconductor material is lower than the efficiency for the blue LED, enter the same power, the optical output power is low.
This situation began to change. Japan and overseas universities and the LED chip makers and others have started to research by changing the surface of GaN crystal growth, a substantial increase in efficiency. GaN semiconductor crystal surface can be changed, there may be green LED Power Supply efficiency is increased to more than 2 times.
GaN semiconductor sales green LED inefficiency reasons is that the piezoelectric field. The piezoelectric field of the electric field generated by the piezoelectric polarization resulting from the stress of the crystal structure. The green LED Spotlight 30W on the market and more based on the polar surface of GaN crystal c-plane (0001) growth surface, its normal direction (c axis) for the growth axis of stratification of GaN semiconductor layer. By changing the growth axis to weaken the piezoelectric polarization of GaN crystal c-plane perpendicular to the non-polar surface as a surface or m-plane or c-plane tilt of the polar surface for the growth of surface per a surface normal direction for the growth axis of the green LED is very active.