Research On GaN Whispering Gallery Mode Microdisk Laser Semiconductor Microcavity Laser

?-nitride semiconductor materials have a wide range of application prospects and development potential in the fields of lighting display,biomedical sensing,optical communications and energy,due to its excellent optoelectronic properties and adjustable band gap,covering UV to NIR.Especially,for gallium nitride(GaN)materials,its wide direct band gap and high exciton confinement energy can make GaN materials show significant advantages in low threshold and high quality factor UV microcavity laser research.In addition,the GaN single crystal micro-nano disk structure has high refractive index and good optical quality characteristics,which can make it a good optical resonator.This can ensure that the total reflection of light on its inner wall forms a gain loop to support a whispering gallery mode(WGM)laser,which can greatly reduce the optical loss due to optical transmission and scattering,leading to reduce the laser threshold and improving the quality factor.At present,there have been many reports about GaN WGM lasers,which include material growth,design of complex structures,process processing,and optical mode analysis.Among them,how to improve the laser emission characteristics and get lower the laser emission threshold effectively is still the focus of research.Therefore,it is necessary to test and study the crystal quality of the GaN microdisk.In this experimental study,GaN microdisks were grown on a substrate using graphene as a two-dimensional buffer layer by hydride vapor phase epitaxy.Since the crystal quality and geometry of gallium nitride will directly affect the optical mode and light emitting characteristics of its microdisk,it also determines whether the laser can be pumped.In addition,the influencing factors of GaN microdisk laser characteristics and optical resonance modes also require in-depth research.The following is the specific content of this paper:1.GaN microdisks were prepared on sapphire and SiC substrates by using HVPE epitaxy,using graphene as a buffer layer.The test and characterization results show that obtained GaN microdisks have a regular geometry and good internal crystal quality,which are suitable as resonant microcavity.In addition,the internal stress of the GaN microdisk obtained on sapphire is only 0.014 GPa,which provides a feasible method for the synthesis,stripping and further integration on laser devices.2.In photo luminescence(PL)experiments,It was confirmed that the GaN microdisks have different modes of light oscillations in different directions,that is,F-P mode signals are received along the C axis direction,and WGM signals are received in the vertical C axis direction.In addition,a multimode laser signal is received under high energy irradiation,with a excitation threshold of 11.5 ?W and a Q value of 3049.The analysis of the optical mode shows that the existence of a Double-triangular whispering-gallery mode(D3-WGM)is confirmed from a nitride microdisk for the first time in the world.The characteristics of the new mode and the conversion mechanism were also studied.The results were considered to be related to the spatial locality of stimulated radiation.Based on this novel laser mode characteristic,microcavity lasers are expected to be further developed and applied in the field of nanophotonics.