Research On Characteristics Of High Temperature And High Power Laser Diode Array Chips And Devices

Due to compact sizes,high output power,high electro-optical conversion efficiency,wide range and easy to control lasing wavelength,long service life,high reliability,laser diodes are extremely widely used in the field of pumping,material processing,medical beauty and military applications.As the demand for laser diodes continue to increase,higher requirements have been placed on the optoelectronic performance and reliability of high-power semiconductor lasers,especially the device applied in high-temperature environment,which face harsh working environment,and largely affect the photoelectric performance and reliability of semiconductor lasers.Since temperature limits the photoelectric performance of laser diodes,researching the main constraints,including the photoelectric performance and reliability of laser diodes is meaningful for the optimization design and reliability research of high-power semiconductor laser.The topic of this thesis mainly focus on simulation optimization and the test characterization of diodes at different temperature,further learning the influence of temperature on the photoelectric performance of the device and the relationship between energy loss and temperature.In addition,through accelerated life aging test,the average life of the device is extrapolated,and the failure mechanism of the device was analyzed.In view of the above topics,the thesis has mainly done the following parts:(1)The epitaxial structure design of high-power laser diodes is one of the key factors affecting the optoelectronic performance of the device.The 9xxnm high-power semiconductor laser array chip which is used for research object,to be analyzed the main factors affecting chip gain,threshold conditions,internal loss,and quantum efficiency.Furthermore,the effects of active region material composition,waveguide layer material composition,and thickness on device performance are clarified.The simulation results show that the optimal Al composition of N-type and P-type waveguide layer and cladding layer,when the chip operating temperature is 60°C and the Al composition of the waveguide layer is 20%,the electro-optical conversion efficiency is the highest.(2)To solve the problem performance degradation of high-power laser chip caused by the increase of operating temperature,and quantify the main factors which affect laser stability,we independently built a high-power laser array chip test system to study 15-60°C the temperature characteristics of the chip.Five energy loss distributions and the changing trends with temperature are analyzed.The experimental results show that when the temperature is increased from 15°C to 60°C,the joule heat loss is reduced from 21.70% to 20.72%,the voltage loss is reduced from 1.50% to1.47%,and the proportion of spontaneous radiation is between 14.84% and 19.14%.The percentage of carrier leakage increased rapidly from 2.3% to 11.36%,which is the key cause of chip thermal instability.This research provides an important reference for improving the electro-optical conversion efficiency of semiconductor laser chips at high temperatures.(3)Focusing on the problems of reduced life and poor reliability of laser diodes driven by high currents,the reliability and failure mechanism of laser diodes were studied,and current step stress accelerated life aging tests were carried out at six different stress points of 500A-1000 A.The experiment uses the inverse power law model to calculate the average life of the device under the condition of 500 A under the condition of 500 A to be 118.58 h.Moreover,microscope,scanning electron microscope(SEM),electroluminescence(EL)images is used to analyze the failure mechanism of the device,and study the reliability of the device.After the experimental analysis,the following conclusions are drawn.According to the SEM and EL image analysis,the failure of the device is mainly due to two reasons: on the one hand,the voltage of the device is roughly broken which cause sudden failure of laser diode;On the other hand,the cavity surface of the device is locally overheated to generate dark spot defect,which causes some of the point of laser not emit light.Because of dark spot defect,the output power of the device is reduced,and the temperature of the cavity surface is further increased,forming a positive feedback and causing the device to fail.