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Parametric numerical study of the modulation transfer function in small-pitch InGaAs/InP infrared arrays with
Optics Express
|March 14, 2018
Summary
We improved the modulation transfer function (MTF) in short-wave infrared photodetectors by adding microlenses. This reduces pixel crosstalk caused by carrier diffusion in indium gallium arsenide (InGaAs) arrays.
Area of Science:
- Optoelectronics
- Semiconductor Devices
- Infrared Imaging
Background:
- Indium gallium arsenide (InGaAs) photodetectors are crucial for short-wave infrared (SWIR) imaging.
- Modulation Transfer Function (MTF) is a key metric for image quality in photodetector arrays.
- Pixel crosstalk can degrade MTF performance in small-pitch arrays.
Purpose of the Study:
- To investigate the factors affecting the MTF in SWIR InGaAs/InP photodetector arrays.
- To analyze the impact of pixel pitch, microlenses, absorber thickness, and doping concentration on MTF.
- To understand the role of photogenerated carrier diffusion in limiting MTF.
Main Methods:
- Utilized a 2D numerical method combining finite-difference time domain (FDTD) for optical simulations and finite-element method (FEM) for drift-diffusion simulations.
- Conducted a parametric study varying key design parameters of the InGaAs photodetector arrays.
- Focused on the correlation between lateral carrier diffusion and MTF performance.
Main Results:
- Small-pitch arrays showed reduced MTF due to pixel crosstalk from long minority carrier diffusion lengths.
- Monolithic microlenses significantly improved MTF across all pitches, especially near cutoff frequencies.
- MTF demonstrated strong dependence on the thickness and doping concentration of the InGaAs absorber layer.
- Reported trends for dark current and quantum efficiency.
Conclusions:
- Microlens integration is an effective strategy to enhance MTF in InGaAs/InP SWIR photodetectors.
- Optimizing absorber thickness and doping is critical for maximizing MTF performance.
- Understanding carrier diffusion is essential for designing high-resolution SWIR imaging systems.
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