Optimization of p-cladding layer and waveguide layer of InGaN-based blue laser diodes
[Objective]For the purpose of improving the performance of InGaN lasers,comprehensive effects of p-cladding layer and waveguide layer on the performance of InGaN-based blue lasers are studied.Results can be used to improve the performance of InGaN-based blue lasers,which can be critically applied in areas such as laser displays,high-density optical data storage and laser processing.The motivation of our research lies in enhancing the carrier confinement of GaN-based laser diodes.Because the hole mobility is smaller than the electron mobility,injection amounts of electrons and holes in multiple quantum wells differ.This difference leads to the leakage of electrons into the waveguide layer.In addition,due to the structural asymmetry of Ⅲ-V nitrides,lasers exhibit strong polarization effects,resulting in band bending and weakening the constraint of quantum wells on carriers.Consequently,numerous optimization ideas have been proposed to solve this problem,but most of them focus on multiple quantum wells and barriers.These results show that p-cladding and waveguide layer also play an important role in the performance of InGaN-based blue laser diodes.[Methods]Based on the experimental sample structure,the InGaN-based blue laser with the same structure is constructed by PICS3D simulation software.The optical output power of the simulated standard structure is compared with experimental results,thus demonstrating the reliability of the subsequent data in this article.A series of InGaN-based blue lasers are constructed,and the optical output power,band structure,optical field distribution and carrier current density distribution of different p-cladding and waveguide structures are compared in order to optimize the photoelectric performance of laser.Also,the p-cladding layer is optimized into a multi-layer Al component gradient structure to reduce the Al component difference at the interface between the p-cladding layer and the electron barrier layer,and the optimal structure under this optimization mode is obtained.On the basis of the aforementioned optimization structure,the In component of the waveguide layer is further adjusted to change the refractive index difference between the waveguide layer and the p-cladding layer,so that the optical limiting ability of the waveguide layer is improved.At the same time,with the increase of In components in the upper waveguide,the band gap of the conduction band decreases,and the band gap difference with the electron barrier layer increases,thus strengthening the electron constraint.Finally,the structure with the best photoelectric performance is obtained by comprehensive comparison.[Results]Firstly,the original structure with the same parameters and structure is set up according to the reference,and its optical power curve and wavelength are also consistent with the experimental sample.Then,the p-cladding layer is optimized into a multi-layer Al gradient structure.With the increase of the number of p-cladding layers and the decrease of the Al component difference between the p-cladding layer and the electron barrier layer,the optical output power and slope efficiency continue to increase,and the output power and slope efficiency of the optimal structure are increased by 21.65％and 21.48％respectively,compared with the standard structure.Secondly,on the basis of the optimization structure mentioned above,the In components of the waveguide layer are adjusted,and the output power of different components is compared.It is found that the optical output power increases conspicuously with the increase of In components of the upper waveguide layer.The final optimized structure is obtained by optimizing both at the same time,the optical output power can reach 0.421 W,which is 65.75％higher than that of the standard structure.[Conclusions]The optimal structure of the p-cladding layer with multi-layer Al component gradient reduces the Al component difference between the p-cladding layer and the electron barrier layer,and can effectively reduce the lattice mismatch and barrier difference between two layers,so that the hole injection in the active region can be improved.Based on the optimization structure mentioned above,appropriately increasing the In component of the waveguide layer can effectively improve the optical limiting factor.Especially,the increase of the In component of the upper waveguide clearly improves the optical limiting factor,the optical field distribution of the optimized structure becomes concentrated,and the electron leakage current density becomes small.All these merits appear conducive toward increasing the radiation recombination in the active region and improving the optical output power of the device.
blue laser diodeInGaN-basedp-cladding layerlinear gradientwaveguide layeroptical limiting factor
万方数据
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