Study Of GaN-based Self-splitting Vertical Structure LED

GaN-based lighting-emitting diode(LED),one of the most promising lighting sources,has many advantages such as energy conservation,environmental protection,high luminous efficiency,small volume and long lifetime.Especially,GaN-based vertical structure LED has solved problems existing in regular sapphire substrate LED.It has high potential in high power GaN-based LED because of its excellent characteristics like good heat dissipation,uniform current distribution,large luminous area,low turn-on voltage and so on.At present,in the fabrication process of GaN-based vertical structure LED,Inductively Coupled Plasma(ICP)is often used to determine the size of device and remove u-GaN layer.In addition,after LED device is fabricated,the metal substrate needs to be cut to achieve the separation of device.However,ICP etching and metal cutting will cause damage to LED device,affecting its performance.In order to solve these problems,this thesis proposes GaN-based self-splitting vertical structure LED.We design the experimental scheme,figure out the process conditions,and characterize the device performance of GaN-based self-splitting vertical structure LED.The main work is summarized as follows:1.Design of experimental scheme:By using the characteristics that the freestanding GaN film can break during laser lift-off,we propose the experimental scheme for GaN-based self-splitting vertical structure LED.After laser lift-off,the size of the device can be determined and the device can be self-separated without metal cutting.In addition,it is not necessary to use ICP etching technology to remove the unwanted GaN film and u-GaN layer.2.Study of process conditions:We explore the process conditions of key technologies for GaN-based self-splitting vertical structure LED,including thick photoresist photolithography process for patterned electroplating,patterned electroplating process,glue bonding process and laser lift-off self-splitting process.3.Device fabrication:For comparison,we use the same epitaxial structure to fabricate GaN-based self-splitting vertical structure LED and regular sapphire substrate LED with the same size.4.Device performance test,simulation and analysis:Compared with regular sapphire substrate LED,GaN-based self-splitting vertical structure LED has lower turn-on voltage and reverse leakage current.In addition,due to the good heat dissipation of Cu,the thermal effect of GaN-based self-splitting vertical structure LED is not obvious under the large injection current;the junction temperature is low;the redshift of peak wavelength and the broaden of FMHM are small;the luminous intensity decreases more slowly.The results show that GaN-based self-splitting vertical structure LED fabricated by the new process method has good photoelectric characteristics and heat dissipation performance.