| In this paper, Pt/CdS ultraviolet and InSb infrared dual-color focal-plane arrays and InSb infrared focal-plane arrays with diffractive microlenses are studied and optimized based on numerical simulation, the aim is to offer theoretical support and practical experience for third-generation infrared technology of InSb focal-plane arrays with features of high sensitivity, huge arrays and multicolour capabilities. The research results show that Pt/CdS ultraviolet and InSb infrared dual-color focal-plane arrays detector can gather data in both ultraviolet and infrared bands to improve its sensitivity and recognition rate. The numerical simulations also prove that diffractive microlens arrays are capable of focusing infrared radiation to InSb photosensitive area. By integrating with diffractive microlens arrays, the quantum efficiency of InSb infrared focal-plane arrays is improved and the crosstalk is reduced effectively. Detailed methods and results are as follows:1、In this paper, hybrid method of combining finite difference time domain method(FDTD) and finite element method(FEM) is used in two-dimensional numerical analysis of designed device. The electromagnetic fields are simulated by FDTD method based on Maxwell’s partial equations. In this step, the database of various material parameters is established firstly, such as electric conductivity, relative permittivity and relative permeability dependent on frequency, and then the simulation region is meshed properly due to the wavelength and device size. At last, the optical generation density distribution in the device is calculated using FDTD method by combining the above parameters and dispersive models. The process of electric simulation by FEM is initialized with the known optical generation density, and combines the mobility, the band gap, absorption coefficient, dielectric constants and other parameters of materials, then calculates the current of the simulation device under zero bias based on the classical drift diffusion model, SRH recombination, Auger recombination and other basic physical models.2、By using the above numerical simulation method, the spectral response of Pt/CdS ultraviolet and InSb infrared dual-color focal-plane arrays are obtained. And the operating band of this structure is 300~550nm in ultraviolet band and 2.9~5.7μm in infrared band. The simulation results prove the dual-band detection capabilities theoretically. Five designs of diffractive microlens arrays are investigated by diffraction optics and phase-matcher approach, they are four-levels with one-zone, five-levels with one-zone, eight-levels with one-zone, sixteen-levels with one-zone, four-levels with two-zone diffractive microlenses. The relationship between the device structural parameters and the quantum efficiency and crosstalk is analyzed by numerical simulation. Research shows that diffractive microlenses have better ability to concentrate lights than spherical refractive microlenses when microstructure size of the detectors is equivalent with wavelength. With the increase of levels in the zones of diffractive microlenses, the quantum efficiency improves and the crosstalk reduces, and the InSb infrared focal-plane arrays with sixteen-levels diffractive microlens arrays have the highest quantum efficiency, 52.0%, when the thickness of diffractive microlense is equal to 165μm. Additionally, the empirical formula revealing the the quantum efficiency dependent on the structure of diffractive microlenses is obtained by fitting the results of InSb infrared focal-plane arrays with different diffractive microlenses. These researches can provide theoretical support for third-generation infrared technology of InSb focal-plane arrays. |
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