高亮度大功率InGaAlP红光LED芯片研制

The Study of High-brightness and High-power InGaAlP Red LED

报道了大功率高亮度InGaAlP红光LED芯片的设计和工艺制备,实验芯片采用环形插指状电极。和传统的LED芯片相比较,环形插指状电极LED芯片电流扩展分布更均匀,而且更有利于与其它器件的集成。对制备好的芯片进行了I-V特性、光谱特性、光通量和光强的测量。芯片的电性能非常好,其开启电压VT为1.5V;当工作电压达到3V时,工作电流为500mA;在工作电流为350mA时,峰值波长为635nm,半峰全宽为16.4nm,光强为830mcd。在色度学测试中,色坐标为x=0.6943,y=0.3056,显色指数为18.4。因此可以得知高亮度大功率InGaAlP红光LED是未来LED作为普通照明光源应用的第一步,而且将会在科学研究和工业投资的很多应用领域中成为新的焦点。

It is reported that the design and fabrication of high-brightness and high-power InGaAIP ring-shaped interdigitated red LED. High-brightness and high-power InGaAIP 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 InGaAIP LED epitaxial layer has six layers. From top to bottom, they are the window layer （p-GaP）, the p clad layer（ p-InGaAIP）, the active layer between clad layers （i-InGaAIP）, the n clad layer（ n- InGaAIP）, 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 mm^2. The fabrication of ring-shaped interdigitated LED chip, essentially, is the same as conventional LED chip, involving photolithography, PECVD SiO2, 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;H2O and H2O2 as an InGaAIP etching solution, and the chip is protected by SiO2 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 N2. 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 InGaAIP 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.