Long Wavelength RCE Photodetector Based On Sub-wavelength Grating

Under the wave of informationization,optical communication has become the main transmission method of communication networks with unparalleled advantages such as long distance,large capacity and high speed.With the advent of the"Broadband China"strategy and the advent of the 5G commercialization era,it has provided an unprecedented opportunity for the development of optical communication.As one of the core devices,the photodetector used in the optical communication system plays a key role in completing the conversion of the photoelectric signal.Therefore,the photodetector with high photoelectric conversion efficiency and high response speed is important for FTTX,Internet,big data and cloud computing.The resonant enhanced photodetector(RCE-PD)used in optical communication systems has the characteristics of high speed and high quantum efficiency,which solves the contradiction between bandwidth and quantum efficiency.For long-wavelength RCE-PD,because of the small difference in refractive index of InP-based materials,it is very difficult to produce high-reflectivity distributed Bragg reflectors(DBRs).In order to solve this problem,this paper proposes a Monolithic high-contrast resonant enhanced photodetector(M-HCG-RCE-PD)based on sub-wavelength grating.M-HCG-RCE-PD was designed and optimized through theoretical analysis,and related process research was carried out to realize the hollow structure of M-HCG-RCE-PD.The research results and innovations of this paper are as follows:1.A monolithic integrated long-wavelength resonant enhanced photodetector based on sub-wavelength grating is proposed.The use of wide spectrum and high reflectivity characteristics solves the problem of long-wavelength RCE-PD in the fabrication of high reflectivity DBRs while achieving monolithic integration.2.A high-contrast sub-wavelength grating(HCG)is designed using the rigorous coupled wave theory(RCWA)to obtain a polarization-sensitive high-reflection mirror structure.When the thickness of the HCG is 0.185?m,the period is 1.07?m,and the duty ratio is 0.4,the reflectivity is>99in the wavelength range of 1.5?m to 1.6 ?m for a transverse electric(TE)polarization incident light.A two-dimensional simulation model of the photodetector is established and optimized.The bandwidth of the M-HCG-RCE-PD is 34 GHz when the device diameter was 20 ?m,and the quantum efficiency at 1550 nm is 82%.3.A new way to optimize the detector bandwidth is proposed.Generally,when optimizing the structure of a multi-layer detector,our usual practice is to optimize one of the layers first.After obtaining the optimal value,we optimize the next layer by fixing this value.However,this may not be very accurate because there is no guarantee that the next layer will be optimized.The previous optimum value is the optimum value,so a method is proposed here,by introducing a parameter K,defined as the ratio of the total intrinsic zone thickness to the absorption zone thickness.The bandwidth optimization of the three-layer resonant enhancement photodetector with two spacer layers and one absorption layer can be completed in one optimization process.4.A process scheme for realizing the M-HCG-RCE-PD hollow structure is proposed.The hollow structure of M-HCG-RCE-PD was successfully prepared by wet etching,and the key parameters were obtained.The collapse problem exist in the hollow structure was solved,at the same time,the side etching rate of the etching solution was measured.