It is reported that the design and fabrication of high-brightness and high-power InGaAlP ring-shaped interdigitated red LED. High-brightness and high-power InGaAlP LED is a new kind of visible light LED developed in recent years

which is driven by large current capacity

high luminous efficiency and excellent heat resistance. It has been used in various fields

such as large area displays

traffic lights

back-lighting

aviation lighting and so on. As compared with the conventional LED chip

the ring-shaped interdigitated LED chip is more flexible to integrate with other devices

and it leads the more uniform current spreading. The InGaAlP LED epitaxial layer has six layers. From top to bottom

they are the window layer (p-GaP)

the p clad layer(p-InGaAlP)

the active layer between clad layers(i-InGaAlP)

the n clad layer(n-InGaAlP)

distributed Bragg reflectors (DBR) and the n-Substrate(n-GaAs). The epitaxial wafer is tested by scanning electron microscope (SEM) and X-ray double crystal diffraction. The results show the interface of materials is flat

and the integrality and quality of the epitaxial wafer are optimum.The size of chip is 1 mm2.The fabrication of ring-shaped interdigitated LED chip

essentially

is the same as conventional LED chip

involving photolithography

PECVD SiO

2

wet etching

evaporation

lift off and rapid thermal annealing using four masks. To control the widths of mesa and n area precisely

the selecting etch technique has been adopted

using HCL;H

2

O and H

2

O

2

as an InGaAlP etching solution

and the chip is protected by SiO

2

and single layer photoresist during the etching. The fabrication of Ⅲ-Ⅴ compound semiconductor p-type Ohmic contact is more difficult than the fabrication of n-type Ohmic contact. So how to fabricate p-type ohmic contact is a second important technology. AuZn/Au is used to be the p-contact metal in this study

and the chips are sintering for 20 s at 400℃ in N

2

.The

I

-

V

characteristics

light emission spectrum

luminous flux

luminous intensity of this LED have been measured. A good characteristic is obtained with turn-on voltage of 1.5 V and forward current of 500 mA at its forward voltage of 3 V. The peak wavelength is 635 nm

which corresponds to red light

and the full width of half maximum is 16.4 nm at injection current of 350 mA. The luminous intensity is 830 mcd. The color coordinates is x=0.694 3

y=0.305 6 and the color index is 18.4. So we will conclude that the high-brightness and high-power InGaAlP red LED is the first step for a wide scope of general illumination with LED in the future

and it will become new focus in both scientific research and industrial investment for its wide application.