研究目的
Investigating the influence of structural and material parameters on the modulation transfer function (MTF) of lattice matched InGaAs/InP planar small pitch arrays to optimize the MTF and suppress inter-pixel crosstalk.
研究成果
Extending depletion zone through deeper junction depth and lower doping concentration in absorption layer contributes to optimizing the MTF and it functions better for smaller pitch array. However, moderate junction depth and doping concentration of absorption layer should be chosen in actual preparation for the reduced specific detectivity brought by extending depletion zone. The impacts of lattice temperature on MTF and crosstalk in detector arrays has also been investigated. And more serious impact on larger pitch arrays has been conformed. The research findings in this work would provide meaningful references for the performance improvement of InGaAs detector dense array system.
研究不足
The inevitable cost of deteriorating the specific detectivity should not be ignored. And hence, junction depth and doping concentration of the absorption layer need to be balanced in actual preparation.
1：Experimental Design and Method Selection:
Three-dimensional numerical simulation technology was used to investigate the influence of structural and material parameters on the MTF of lattice matched InGaAs/InP planar small pitch arrays. The finite-difference time-domain (FDTD) method was used to analyze the electromagnetic field of the device under illumination and the absorbed photon density distribution was calculated. Then the results of FDTD were used to calculate the distribution of photo-generated carriers. Subsequently, photo-generated carrier concentration was introduced into the Poisson equations and the carrier continuity equations for electrical analysis. Then they were solved through the finite element method (FEM) method to obtain the final optical response of the device.
2：Sample Selection and Data Sources:
Three-dimensional 3 × 3 InGaAs detector arrays with pitch of 15 μm, 10 μm and 5 μm were modeled to capture the behaviors of MTF, quantum efficiency and dark current density.
3：List of Experimental Equipment and Materials:
The structure parameters of InGaAs on InP DLPH photodetector in the simulation were listed. The doping concentration of absorption layer and the lattice temperature were kept at 1 × 1016 cm?3 and 300 K respectively.
4：Experimental Procedures and Operational Workflow:
The Gaussian light source with beam waist radius of 3.0 μm was utilized in MTF simulation. Both of light sources were kept with the incident wavelength of 1.5 μm and photon densities of 1014 photons cm?2 s?1. During moving Gaussian beam from the central pixel to the nearest neighboring pixel, the photocurrents of the central pixel were collected as the scan profile. Then the MTF of detector array could be obtained through Fourier transform.
5：0 μm was utilized in MTF simulation. Both of light sources were kept with the incident wavelength of 5 μm and photon densities of 1014 photons cm?2 s?During moving Gaussian beam from the central pixel to the nearest neighboring pixel, the photocurrents of the central pixel were collected as the scan profile. Then the MTF of detector array could be obtained through Fourier transform.
Data Analysis Methods:
5. Data Analysis Methods: The MTF is the most important parameter considered in the imaging system. The MTF of infrared detector focal plane arrays evaluates the transform ability of different spatial frequency components of the object. The higher MTF represents the more imaging accuracy for objects, which is sensitive to the collection and diffusion of photo-generated carriers.
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