Study On The Mechanism Of Gallium Nitride Material Processing Based On Femtosecond Laser

Gallium nitride(GaN)is a typical third-generation semiconductor material,which has a very important application value in high frequency,high power electronic devices,blue light,green light,ultraviolet and other optoelectronic devices.However,GaN material has high hardness and chemical stability.Therefore,it is difficult to fabricate large size microstructure on GaN surface.At present,dry etching is often used to process GaN materials.However,dry etching needs to be combined with lithography mask technology,which leads to complex processing technology,high technical threshold and slow processing rate of microstructure.Therefore,it is of great significance to study the preparation of GaN surface microstructure.In view of the existing problems in the surface microstructure fabrication of GaN materials,a femtosecond laser combined with wet and dry etching method is proposed to realize the surface microstructure fabrication of GaN materials.In this method,the special properties of femtosecond laser are used to destroy the target material,and laser ablation craters are induced on GaN surface centered on the operation point of femtosecond laser.Then wet etching or ICP dry etching is used for further processing to realize the machining of GaN surface microstructure.Effectively solve the complex problems of lithography technology.The main research contents and results of this paper are as follows:(1)The changes of microstructure and chemical composition of GaN after laser irradiation were studied by femtosecond laser technology.The periodic nanofringes formed on the side walls of ablative craters and the effects of irradiated craters' side walls on subsequent etching were explored.(2)The surface microstructure of GaN was prepared by femtosecond laser technique combined with the wet etching of potassium hydroxide(KOH)solution.The etching mechanism of GaN surface with different polarity after femtosecond laser processing was analyzed,and the influence rules of femtosecond laser processing parameters,wet etching parameters of KOH solution and GaN materials with different polarity on the final etching structure were explored.Finally,the hexagonal microstructure on GaN surface with different polarity surfaces was prepared.The feasibility of femtosecond laser wet etching to fabricate microstructure on GaN surface was verified.(3)Based on the femtosecond laser-assisted Inductively Coupled Plasma(ICP)dry etching technology,the influence of different gas velocities on the etched structure morphology was studied.In the experiment,by changing the etching gas flow rate,the microstructure morphology of GaN material surface and the surface roughness of the etched material were controlled.The influence of different femtosecond laser processing parameters on the ICP etched microstructure was analyzed and studied.By changing the number of femtosecond laser pulses and the laser energy,the oxygen content deposited on the surface of the material can be adjusted to realize the preparation of microstructures with different morphologies.Then,the effect of oxygen on the ICP etching structure was eliminated by changing the femtosecond laser processing environment,and the effect of oxygen on the ICP etching structure was verified.