Research On Generation Mechanism And Characterization Of Low-frequency Noise In High Power Semiconductor Laser Diodes

With the development of theoretical research and fabrication technology,High-power Semiconductor Laser Diodes(HP-LDs)have been widely used in military,industrial processing,laser medical treatment,optical communications,optical storage and other fields due to its high conversion efficiency,small size,light weight,direct modulation and easy integration with other semiconductor devices.In recent years,with the increase of the output optical power of high-power semiconductor laser diodes,new active materials are emerging and the application fields are expanding day by day.Researchers put forward higher requirements for the reliability of high-power semiconductor laser diodes,which makes the use of low-frequency noise as the reliability evaluation method of high-power semiconductor laser diodes attract more attention because of its advantages such as convenience,lossless and fast speed.Moreover,low-frequency noise,as a universal physical phenomenon in high-power semiconductor laser diodes,is the external manifestation of the micro movement of its internal carriers.The connection between the internal phenomenon and the external manifestation is bound to better reflect its micro properties to promote the development of HP-LDs in material growth,chip preparation and other technologies.However,the noise model of low-frequency noise(mainly 1/f noise)of HP-LDs is still incomplete,and compared with other conventional semiconductor devices,there is a unique low-frequency 1/f optical noise in HP-LDs,and its low-frequency noise phenomenon and mechanism are more complex,which contains more useful information leading to degradation and failure of HP-LDs and can guide its reliability management.In order to use the low-frequency noise of HP-LDs to achieve non-destructive characterization of its reliability and device quality screening,low-frequency noise generation mechanism and characterization of high-power semiconductor laser diodes are studied in this thesis.By combining theoretical modeling,simulation and experimental testing,the related researches on the mechanism and characteristics of noise in HP-LDs,the1/f noise model and its generation mechanism of HP-LDs under small injection,the junction-voltage 1/f fluctuation model of HP-LDs under lasing state and the quantum correlation between it and photon-number fluctuation,and the characterization of low-frequency noise of HP-LDs are carried out.The main contents and results of this thesis are as follows:1.Study on the generation mechanism and characteristics of 1/f noise in double heterojunctions HP-LDs.Based on the classical Langevin equation,the transport mechanism and drift process of minority carriers in HP-LDs with single and double heterojunctions are analyzed.Two mechanisms related to the junction-current noise of HP-LDs,namely the thermal fluctuation of minority carriers and the generation-recombination noise,are discussed.The noise equivalent circuit models of HP-LDs with single and double heterojunction are established,respectively.On this basis,parasitic parameters and active region parameters were introduced to establish the equivalent circuit model of double heterojunction HP-LDs,and the 1/f noise model caused by the fluctuation of contact resistance and packaging lead resistance was derived.The theoretical model and experimental results are compared to verify the accuracy of the model,and the noise characteristics and mechanism of 1/f noise in double heterojunction HP-LDs are further analyzed and discussed.2.Study on 1/f noise model and its generating mechanism of HP-LDs under small injection.Under the condition of small injection,the 1/f noise model of HP-LDs is theoretically derived based on the surface recombination as the main transport mechanism,and the carrier degeneracy,high level injection and non-radiative recombination are considered.It is found that the formation mechanism of 1/f noise under small injection was similar to that of the non-radiative recombination current caused by defects,impurities and displacements.Using electroluminescence as non-radiative current,the changes of surface state,1/f noise characteristics and electrical characteristics of HP-LDs,such as P-V and I-V characteristics,are studied during the aging test under small injection.The effectiveness of1/f noise to characterize the surface stability of HP-LDs is verified,and the basis for the surface quality evaluation of HP-LDs is provided.3.The junction-voltage 1/f fluctuation model of HP-LDs in lasing state and the quantum correlation with photon-number fluctuation.Based on the Quantum-mechanical Langevin equations,a theoretical model of junction-voltage 1/f fluctuation in HP-LDs is established,and its physical mechanisms is discussed.Based on classical Quantum-mechanical processes such as stimulated radiation and spontaneous emission in laser theory,it is proved that current-driven HP-LDs can suppress the pumping noise and produce the phase minimum uncertainty state in the frequency region below the cavity width.The near-particle number phase minimum uncertainty state(the amplitude-squeezed state)produced by HP-LDs is obtained.The amplitude noise is reduced due to the suppression of pumping noise and the high quantum efficiency.Meanwhile,the quantum correlation between the photon-number fluctuation from the external field and the junction voltage 1/f fluctuation is predicted theoretically.The theoretical prediction and experimental results of the correlation factors are compared.The experimental results are in good agreement with the theoretical prediction,which verifies the correctness of the theoretical prediction.4.Characterization of low-frequency noise in high-power semiconductor laser diodes.The correlation between the low-frequency optical and electrical noise for reliability characterization of 808 nm HP-LDs is proposed.The feasibility and effectiveness of the correlation between low-frequency optical and electrical noise as a reliability evaluation tool are verified by experiments.In view of the destructiveness of traditional accelerated aging test to devices and the lack of comprehensive screening results by using single initial measurement noise as a single screening index,a pre-screening method combining low-frequency noise measurement and accelerated aging test of VCSEL devices is proposed.The pre-screening model of VCSELs is established,and the correctness of the model is verified by experiments.The degradation mechanism of radiation effect and the characterization of radiation damage of HP-LDs based on 1/f noise are discussed.A 1/f noise characterization model of HP-LDs with radiation defects is established.Meanwhile,the effects of radiation on the characteristics of HP-LDs are discussed.In this thesis,the established 1/f noise models and the proposed characterization methods for high-power semiconductor laser diodes are verified to be effective through the comparison between simulation analysis and experimental results,which provides a solution for the research on non-destructive reliability characterization and quality screening of high-power semiconductor laser diodes.