Design And Fabrication Of Silicon Based Epitaxial Ⅲ-Ⅴ Laser Chip Structure With Low Differential Resistance

With the gradual advent of the digital and information era,the amount of data also presents explosive growth,which means that the traditional electronic technology based on electric signal is gradually limited.However,the photons have the properties of non-chargeability and noninterference,so there was no limitation of bottleneck effect when they were used as information carriers either in free space or in dielectric waveguides for transmission.Silicon-based microelectronics integrated circuits have fully matured for large-scale applications,combining photonic devices and silicon-based microelectronics technology can give full play to the mature silicon process and the advantages of photonic devices such as high-speed,strong anti-interference and low-power consumption.Currently,detectors,modulators and other devices have been used in optoelectronic monolithic integration,and silicon-based lasers as light sources have also made significant breakthroughs and are gradually moving toward practicality.However,most of the most widely used silicon-based lasers are bonding silicon-based lasers,and the direct epitaxial silicon-based lasers which are the most promising for large-area optoelectronic monolithic integration and cost reduction,have also made significant progress.But there were still problems such as poor stability and serious heat generation,which will significantly reduce the performance of silicon-based laser devices and limit the application of silicon-based lasers to some extent.Based on the above background,this thesis aims to improve the optoelectronic performance of silicon-based lasers as the main goal,and to optimize the laser chip structure as the method to achieve the preparation of lowresistance,high-performance silicon-based lasers.This paper focuses on the structural design,process preparation and performance measuring ofⅢ-Ⅴ quantum dot lasers epitaxially grown on silicon.The main research contents and results are as follows:1、A scheme to reduce the differential resistance by shortening the transverse distance between the positive and negative electrodes of coplanar electrode chip structure was proposed.By optimized design of the conventional cathode structure,the ridge waveguide lasers were fabricated by using this structure on on-axis silicon.The F-P lasers with a cavity length of 2.0 mm and a stripe width of 15 μm achieved a single-facet output power of 24 mW,the threshold current density was 426 A/cm2,the slopeefficiency was 0.071 W/A,the differential resistance was 6.3Ω,and the maximum wall-plug-efficiency was 0.71%.The characteristic temperature of the laser was 24.7 K in the operating temperature range of 20℃ to 65℃.The lasing wavelength of the lasers was red shift from 1301 nm to 1317 nm when the injection current was increased from 1.38 to 3.85 times the threshold current.2、A symmetrical cathode structure design with a parallel form is proposed,and a low differential resistance laser chip was prepared with an optimized process.Test results show that the devices achieved roomtemperature continuous-wave operation,the lasers with a cavity length of 1.5 mm and a stripe width of 50 μm achieved a single-facet output power of 70 mW,the threshold current density was 496 A/cm2,the slopeefficiency was 0.074 W/A,the maximum wall-plug-efficiency was 2.21%.And the differential resistance was 1.52 Ω,which is the lowest value for international lasers on on-axis silicon.The characteristic temperature of the laser was 43.4 K in the operating temperature range of 15℃ to 45℃.Compared to the conventional cathode structure,the symmetrical cathode structure can significantly reduce the device differential resistance by about 75%,which results in an increment of characteristic temperature from 27.2 K to 43.3 K.In addition,the slope efficiency and maximum wall-plugefficiency were increased by 26.4%and 4.7 times,respectively.Besides the wavelength red shift was reduced by about 77%when the injection current was increased from 1.2 to 2.8 times the threshold current.Therefore,lasers on silicon performance can be significantly improved by using symmetrical cathode structures,which provides an optimized technical solution for fabricating high-performance silicon-based epitaxial lasers.