Study On Optical Mode Of Triangular Ridge Optical Cavity Of Nitride Semiconductor

In GaN/GaN quantum wells of GaN-based materials,by flexibly controlling the metal Indium composition in them,the luminescence band of the quantum wells can be adjusted in the range of ultraviolet to visible light,it is currently an ideal light source material,which is widely used in various of different types of light-emitting devices.The ridge laser prepared based on GaN material can limit the light from the lateral and vertical directions,and can significantly reduce the threshold current.However,most of the traditional ridge lasers use rectangles as their cross-sectional shapes,and there are few reports about using triangles as their cross-sectional shapes.The triangular ridge has the following advantages over the traditional rectangular ridge:the geometric symmetry of the rectangular ridge is relatively high,so the cross-sectional light field distribution is relatively uniform,which results in insufficient excitation intensity;the triangular ridge has lower geometric symmetry,so its light limitation is more uneven,which helps to concentrate the light field energy at the required position to obtain greater excitation intensity.Through the research on the light field distribution of the traditional rectangular cross-section ridge laser,researchers explored the influence of the thickness of each layer,the ridge structure etching depth,the ridge structure width and other factors on the light field distribution in order to improve its structural parameters.Therefore,for the new GaN-based triangular ridge structure,it is important to explore the relationship between the cross-sectional light field distribution and the structure size,which can help improve the structure parameters and increase the excitation intensity.In this paper,the FDTD method was used to study the GaN-based triangular ridge structure on the Sapphire substrate.The light field distribution of GaN-based triangular ridges under different apex angles were analyzed.The relationship between the maximum electric field intensity and the apex angle was studied.The relationship between the average of the electric field intensity near the active area and the apex angle was analyzed.The waveguide mode distribution of the cross section was studied.Finally,the light field distribution and the increase of the maximum electric field intensity in the GaN-based and AlGaN-based triangular ridges covered with Si O₂ and Al films were analyzed.The main contents of this study and the results obtained are as follows:?1?The light field distribution of the GaN-based triangular ridge structure at 450nm under different apex angle conditions was studied.The results show that the GaN-based triangular ridge structure can effectively concentrate the light field energy on the top of the triangular ridge structure.When the angle of the apex angle is small,only one light field energy maxima region generated above structure,the light field energy concentration is high;as the angle of the apex angle increases,the number of light field energy maxima region begins to increase,and the degree of light field energy concentration decreases.?2?The relationship between the maximum electric field intensity of the GaN-based triangular ridge structure and the apex angle was studied at 450 nm.The results show that when the apex angle is less than 40 degrees,the maximum electric field intensity increases with the increase of the apex angle.When the apex angle is greater than 40 degrees,the maximum electric field intensity remains basically unchanged.This is consistent with the law of the number of light field energy maximum regions.?3?The relationship between the average of the electric field intensity near the active region of the GaN-based triangular ridge and the apex angle was studied at 450nm.The results show that the average of the electric field intensity near the active area is basically constant with the increase of the apex angle at first,and then the oscillation gradually increases.When the apex angle is less than 60 degrees,the light field distribution near active region is relatively uniform.?4?The light field distribution of the GaN-based triangular ridge covered with Si O₂and Al films was studied at 450 nm,and the enhancement of the maximum electric field intensity was analyzed.The results show that the additional thin film makes the light field energy in the GaN-based triangular ridge structure more concentrated,and the maximum electric field intensity is greatly enhanced.The maximum of the electric field intensity gradually increases with the increase of the thickness of the Al film and eventually tends to remain unchanged,and increases first and then decreases as the thickness of the Si O₂ film increases.When the thickness of Si O₂ film is about 20 nm and the thickness of the Al film is greater than 40 nm,the maximum of the electric field intensity reaches a maximum value,which can be increased by about 60%.?5?The light field distribution of AlGaN-based?0.7Al composition?triangular ridges covered with Si O₂ and Al films was studied at 280 nm,and the enhancement of the maximum electric field intensity was analyzed.The results show that the additional thin film significantly increases the maximum electric field intensity of the AlGaN-based triangular ridge.The maximum of the electric field intensity gradually increases with the increase of the thickness of the Al film and eventually tends to remain unchanged,and increases first and then decreases as the thickness of the Si O₂ film increases.When the thickness of Si O₂ film is about 10 nm and the thickness of the Al film is greater than 40 nm,the maximum of the electric field intensity reaches a maximum value,which can be increased by about 50%.