Optical Field Distribution And Properties Under High Excitation Of GaN-Based Ridge Structure

Group ? nitrides have good application prospects and research in high-frequency high-temperature devices because of virtue of high exciton binding energy,high breakdown electric field and high saturation electron mobility.At the same time,Group ? nitrides are direct bandgap semiconductors,which also have great research potential in optoelectronic devices.GaN-based lasers can be used in the ultraviolet range,so they are widely used in biomedical,high-density data storage,laser illumination,laser printing,and laser spectroscopy.In terms of LEDs,Group ?nitrides can directly convert electrical energy into light energy,avoiding energy loss,and having high quantum efficiency,providing a more efficient means of illumination.The ?-? compound GaN is a wide and direct band gap semiconductor,which has great research potential.So far,various GaN-based devices have been developed,such as ultraviolet sensors,blue and ultraviolet light-emitting diodes,optical pumping structures,photodetectors,and heterostructure field effect transistors.Among the nitride ridge devices,the principle of carrier absorption of light is the basis of many devices.However,related research has not extended to the stage of high photon density and high carrier density.At present,more and more optical devices are used at high power,so it is especially important to obtain the absorption law at high photon density.Therefore,the light absorption properties of semiconductors at high photon densities have attracted a lot of attention in recent years.Based on the importance of the law of variation of absorption coefficient at high optical density,this paper focuses on the variation of the optical absorption coefficient of InGaN/GaN quantum well structures under high-density photons.In this paper,we proposes a new structure,namely the triangular ridge structure,and explores the limitation of the triangular ridge structure on the light field.The following is the research content and results:(1)Through experiments,we know that when obtaining the vertical and smooth square ridge structure of the sidewall,it is necessary to use the metal Ni and Si02 as a mask.When the RF power is 100 W,it is more advantageous to form a vertical square ridge sidewall.(2)By using the different excitation areas with the same laser power at room temperature,the absorption coefficient is not constant at high photon density but decreases with the increase of photon density.Due to saturation absorption,the absorption coefficient decreases with the increase of photon density.(3)Through FDTD simulation,the triangular ridge structure has better limitation on the light field than the square ridge structure.By changing the angle of the apex angle,it is found that the limitation of the light field is best when the apex angle is less than 30°.(4)The triangular ridge structure with an angle of less than 300°can be obtained by the ICP etching conditions of flow rates of C12,BCl3,and Ar of 20,8,and 5 sccm,ICP power of 1500 W,RF power of 100 W,and pressure of 10 mTorr.(5)According to the PL spectrum of triangle ridge structure and the bare chip,we can find the integrated intensity of both increases with the increase of excitation power.The results confirmed that the triangular ridge structure is precisely due to the limitation of photons at the top end,which can effectively improve the luminous intensity of the quantum well.(6)By comparing the half-width of the bare chip and triangular ridge structures with the power change,we can see that the low-energy peak hasappeared in the triangular ridge structure at the excitation power of 0.0125mW,however the low-energy peak appears in the bare chip when the excitation power is 1.25mW.This result verifies that the triangular ridge has a limiting effect on the light field.Through the above research,on the one hand,we have mastered the preparation method of square ridge and triangular ridge structure.It is confirmed by experiments that the effect of the absorption coefficient reduction needs to be considered under high photon density,which is meaningful for the design and application of high power optoelectronic devices.On the other hand,we got the conclusion that an effective light field limitation can be formed when the apex angle is 30°.