高功率转换效率905 nm垂直腔面发射激光器的设计与制备

Design and fabrication of 905 nm vertical cavity surface emitting laser with high power conversion efficiency

通过对影响垂直腔面发射激光器(vertical cavity surface emitting laser, VCSEL)的功率转换效率的因素进行理论分析,得出斜率效率是影响功率转换效率的主要因素的结论.为获得高功率转换效率,通过对有源区量子阱、P型和N型分布布拉格反射镜(DBR)等进行优化,设计出了905 nm VCSEL的外延结构并进行了高质量外延生长.成功制备出了不同氧化孔径的905 nm VCSEL器件,获得的最大斜率效率为1.12 W/A,最大转换效率为44.8%.此外,探究了氧化孔径对VCSEL的远场和光谱特性的影响.这种具有高功率转换效率的905 nm VCSEL器件为激光雷达的小型化、低成本化提供了良好的基础数据.

Vertical cavity surface emitting lasers(VCSELs)have lots of excellent properties,such as circular beam,low threshold,single longitudinal mode,high speed modulation and monolithic array fabrication capability.The VCSELs have been widely used in data communication and short-distance optical interconnection.In the fields of distance detection and automatic driving,high accuracy lidars have become an indispensable component.In practical applications,905 nm laser exhibits little absorption by the water vapor in the air.In addition,the 905 nm laser can match with both inexpensive Si detector and high response avalanche photodiode(APD).Therefore,the 905 nm semiconductor laser has become a key light source of lidar.This paper presents the design and fabrication of 905 nm VCSEL with high power conversion efficiency.First,the main factors influencing the power conversion efficiency(PCE)of VCSEL are analyzed theoretically.It is concluded that the slope efficiency contributes to the PCE most.In order to achieve a high slope efficiency,strained InGaAs is used as a quantum well material.Due to the wavelength redshift caused by the thermal effect,the lasing peak wavelength of the multiple quantum well(MQW)is designed to be about 892 nm by optimizing the In composition.The active region consists of three pairs of In0.123Ga0.88As/Al0.3Ga0.7MQWs.The N-distributed Bragg reflectors(DBRs)are designed to have 40 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As,and the P-DBRs are designed to have 20 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As.The epitaxial structure is designed and grown by metal organic chemical vapor deposition(MOCVD).The cavity mode of the epitaxial wafer is around 903.7 nm.The photoluminescence(PL)spectrum is also measured.The peak wavelength is approximately 893.7 nm,and the full width at half maximum is 21.6 nm.Then,the 905 nm VCSELs with different apertures(6–18μm)are fabricated via semiconductor technologies such as photolithography,evaporation,inductively coupled plasma(ICP),wet oxidation,electroplating,etc.Finally,the L-I-V characteristics and spectra of VCSELs with different apertures are tested.The obtained maximum slope efficiency and PCE of the devices are 1.12 W/A and 44.8%,respectively.In addition,the influences of aperture size on the far-field profiles and spectra of the devices are investigated.These 905 nm VCSELs with high PCE are potential for the miniaturization and lowing the cost of LiDAR.