Fabrication And Characteristics Of InGaAs/AlGaAs Infrared Light-emitting Diode

Light-emitting diode(LED)as an electroluminescent light source,green environmental protection,small volume,long service life,low power consumption and have incomparable advantages over traditional light sources.In recent years,infrared night vision system has been developed rapidly and widely used in the field of security monitoring.At the same time,Windows10 began to support the iris recognition function,which greatly promoted the development of related industries.This puts forward higher requirements for the infrared light source.The high-power 850nm infrared LED has many excellent properties such as high brightness,low energy consumption,long life,good heat dissipation and so on,which has become the focus of research in various countries.Ternary Al_xGa_1-xAs alloy semiconductors are direct band gap materials when Al components is less than 0.45.InGaAs/AlGaAs quantum well is used as the luminescent material of 850nm infrared LED,which has higher radiation composite efficiency,and has become a common luminescent material for the preparation of infrared LED devices.The photoelectric efficiency of InGaAs/AlGaAs infrared LEDs based on conventional Ga As substrates is very low because the Ga As substrate is will absorb the light from the active region to the substrate.At the same time,the electrical and thermal conductivity of Ga As substrate is poor,which will further reduce the photoelectric efficiency of LED,and at the same time,the heat dissipation performance is poor,which seriously affects the application stability of high-power 850nm infrared LED.Metal substrate has high electrical conductivity,thermal conductivity and high reflectivity.It is a common technology to prepare high-power InGaAs/AlGaAs infrared LED by stripping the original Ga As substrate and transferring it to the metal substrate.The substrate transfer process of high-power 850nm infrared LED generally adopts wafer level bonding technology,but this technology has high technological requirements and low yield,only reaching about 50%.In view of the problems existing in wafer level bonding technology,we have developed a metal substrate LED process suitable for industrial production,and adopted a new technology for preparing metal copper substrate based on electroplating technology,which has overcome the disadvantages of conventional bonding technology and greatly improved the product performance and chip yield(up to 80%).In this paper,the 850nm infrared LED epitaxial structure of InGaAs/AlGaAs multi-quantum well structure is designed and optimized.Combined with substrate stripping process and acid copper plating process,a new LED process of composite metal substrate is developed.The process is simple,high yield,and high power and high efficiency 850nm infrared LED devices are obtained.The main research work includes:1.The design of 850nm infrared LED epitaxial structure:Based on literature investigation and theoretical calculation,the epitaxial structure of LED,including Ga As substrate,In Ga P corrosion stop layer,Al Ga As barrier layer,InGaAs/AlGaAs multi-quantum wells,Ohmic contact layer and Ga P window layer,was determined.In this paper,the matching problem of doping concentration of p-type and n-type Al Ga As barrier layer and quantum well is studied.The PL test method combining electric injection and light injection is used to study the optimal doping concentration of p-type and n-type Al Ga As barrier layer,which effectively improves the internal quantum efficiency of LED.2.Fabrication scheme of InGaAs/AlGaAs infrared LED devices with composite metal substrates:The process includes Ga As substrate etching,acid copper plating,electrode ohmic contact,and channel etching.We have optimized the ohmic contact of the electrode,and obtained the Zn/Au/p-Gap electrode with low contact resistivity.Au/Ni/Au/Cu(100nm/20nm/100nm/50?m)composite metal substrates were determined by considering the reflectivity,thermal performance and contact performance of the metal substrates.Au/Ni/Au was used as the contact electrode and reflection layer,and Cu was used as the supporting substrate.The copper substrate with graphic structure was prepared by lithography and acid copper plating process,which was consistent with the chip size and did not require subsequent scratching.3.The device performance test of Al Ga As/In Ga As infrared LED with metal substrate:The photoelectric properties and thermal stability of InGaAs/AlGaAs infrared LEDs with metal substrate and conventional InGaAs/AlGaAs infrared LEDs were compared.The photoluminescence(PL)and electroluminescence(EL)tests were carried out.The junction temperature,peak wavelength,half-height width and optical power of the two groups of LED samples were analyzed.The results show that the PL integral strength of IRLEDs with metal substrate is increased by about 30%compared with that of conventional IRLEDs,the forward voltage drop is reduced,and the junction temperature increases more slowly with the current.Compared with conventional InGaAs/AlGaAs infrared LEDs,the power of electroluminescence is increased by66.2%and 95.4%at 20m A and 350m A,respectively.The results show that the photoelectric efficiency and thermal stability of LED with composite metal substrate are effectively improved,making it an ideal choice for the development of high-power and high-light efficiency infrared LED.