Research On Quantum Well Intermixing Technology And Application To High Power Semiconductor Lasers

With the advantages of small size,light weight,simple structure,high reliability and excellent photoelectric conversion efficiency,semiconductor lasers have been widely used in communications,industrial processing,military,medical and other fields.High output power and long-term reliability of semiconductor lasers are widely used as a prerequisite,the reliability and high output power of semiconductor lasers are limited by catastrophic optical damage（COD）.The root cause of COD is the high power density of the cavity surface when the laser is working as well as light absorption leading to a rise in cavity surface temperature,cavity surface temperature caused by band gap contraction,band gap contraction exacerbated the light absorption,the vicious cycle of the final cavity surface damage,laser failure.Non-absorbing window（NAW）is one of the methods to effectively suppress the optical absorption at the cavity surface and enhance the COD threshold of semiconductor lasers,while quantum well intermixing（QWI）technique is a simple and low-cost method to fabricate NAW.In this paper,we enhance the device COD threshold from three aspects:epitaxial structure design,process technology,and device fabrication.The main research contents and research results are as follows:（1）The epitaxial structure of a semiconductor laser is simulated.The waveguide structure of the epitaxial wafer is mainly simulated and designed.By the epitaxial structure of unsymmetrical large optical cavity,the output spot size can be increased,the optical power density can be reduced,and the COD threshold can be improved.In addition,compared with the large cavity structure,the unsymmetrical large cavity structure can reduce the waveguide loss,reduce the fundamental mode limiting factor,increase the output power,reduce the far field divergence angle,and increase the effective output optical power of the laser.（2）The basic theory and methods of QWI are studied.The QWI generation conditions are analyzed in detail,and two types of QWI generation methods,impurity free vacancy diffusion（IFVD）and impurity induced diffusion（IID）,are used to study the 980 nm Ga In As/Ga As quantum well semiconductor lasers.The effects of annealing temperature,annealing time,dielectric film type and deposition thickness on QWI are investigated by sputtering SiO₂ films and SiO₂-Cu composite films on the epitaxial wafer surface,respectively,and the results are characterized by photoluminescence（PL）spectrum.The results show that,compared with sputtered SiO₂ film samples,sputtered SiO₂-Cu composite film samples can achieve high efficiency QWI of Ga As-based materials,and multi-cycle annealing is used to enhance the PL intensity after annealing.（3）The semiconductor laser with non-absorbing window is fabricated.A scheme for preparing a non-absorbing window semiconductor laser is designed and verified by simulation,with a laser cavity length of 2 mm,a width of 100μm,and a front and rear window area width of 30μm.For comparison with a semiconductor laser with non-absorbing window,a conventional semiconductor laser is also prepared.The results show that compared with conventional semiconductor lasers,the COD threshold of NAW semiconductor lasers is increased from 0.94 W to 1.78 W,which is an 89%improvement.