Study On Photoelectric Properties And Electrical Aging Reliability Of GaN-Based Green LED On Silicon Substrate

GaN-based LED is widely used in green lighting and microelectronics because of its advantages of moisture resistance,shock resistance,long life,energy conservation,environmental protection and full color.Researchers pay more and more attention to its market.Especially in high-quality display,lighting applications and so on,the white LED is in the manner of light conversion,which is fabricated by coating phosphors on the chip of blue LED,having the problems of large proportion of blue light,lack of cyan-blue light and insufficient red light.High-quality full-spectrum LED lighting technology without phosphor will be the mainstream of LED lighting.This LED is generally composed of multi-primary color LEDs.Among them,the EQE of GaN-based blue LED is over 80%,while that of green LED is only about 40%.The main reason is the"Green Gap",that is,the luminous efficiency is lower than that of other colors between 500nm and 580nm,which is also a problem that researchers have been trying to solve recently.Also,its low reliability seriously limits its application in display and other fields.Therefore,as an important part of phosphor-free LED,it is necessary to study the luminous efficiency and reliability of green LED.In this paper,the effects of the number of quantum wells and the thickness of p-AlGaN electronic barrier layer on the photoelectric properties of green LED are studied.In addition,the electrical aging reliability and failure mechanism of GaN-based green LED on Si substrates are also studied.The main conclusions are as follows:1.InGaN-based green light-emitting diodes?LEDs?with different green quantum well numbers grown on Si?111?substrates by metal organic chemical vapor deposition are investigated.It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9,and results in larger reverse-bias leakage current.Meanwhile,in the case of the sample with the number from 5 to 7 then to 9,the external quantum efciency increases frstly,and then decreases.These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits.2.InGaN based green light-emitting diodes?LED?with different thickness of p-AlGaN electron blocking layer?EBL?grown on Si?111?substrates are investigated.It is found that the thickness of EBL plays an important role in the transport of carriers,especially hole transport.Two side peaks were observed at low temperatures and high current densities,which were emitted by SLs layer and green MQWs close to n-type layer in the LED structure.Thicker p-AlGaN can not only shield penetrating dislocations,but also assist hole injection into deeper quantum wells,thus improving the quantum efficiency and ESD performance of devices.3.The electrical aging mechanism of green LED with the same epitaxy structure was studied,and the influence of NH₃ concentration on the electrical aging performance of green LED was analyzed.The results show that the quantum wells grown at higher NH₃ concentration have more serious In segregation,which leads to greater optical decay and leakage current.