Recent Advances in Infrared Photodetectors

Dear Colleagues,

III-V InGaAs photodetectors have been serving as the key element for ground and space light sensing applications in the short-wavelength infrared (SWIR) band. While InGaAs photodetector assemblies are available in the form of both single-element and focal plane arrays (FPAs), variable spectral response ranges with a cut-on wavelength of 400 nm and cutoff wavelengths of 1.4, 1.65, 1.9, 2.2, and 2.5 μm are also feasible by tailoring the structure and the compound composition. Improvements in the control of the defect density in material epitaxy as well as the optimized device design have led to extremely low dark current levels that surpass rule 07 for both the lattice-matched and the lattice-mismatched detector types. Moreover, driven by demand for higher resolution SWIR imaging, the array format of a single InGaAs FPA chip is continuously enlarged from 320×256 / 640×512 to 4096×4094 with a fine pixel pitch down to 5 μm. Apart from the progress mentioned above, new functionalities and routes for performance enhancement are also demonstrated by integrating with micro/nano-scaled structures, e.g., the monolithic integrated subwavelength grating at the pixel level for polarization light detection and the Mie-type surface resonators for responsivity enhancement. Novel sensing applications have also emerged by utilizing the fingerprint spectral features of materials in the SWIR band, such as biology and medical diagnostics in the NIR-I and NIR-II regions, cultural relics identification, oil and gas pipeline inspection, etc.. In addition, advanced read-out integrated circuit (ROIC) designs, such as the pixel-level Analog-to-Digital Converter (ADC) and the monolithic image processing algorithms have enabled a higher frame rate, larger dynamic range and simplified electronics for cameras.

This Special Issue aims to address issues that involve the materials as well as the device design, the processing technology, the characterization, and the applications of InGaAs photodetectors featuring novel structures, higher performances and new functionalities. This includes:

• Short-wavelength infrared (SWIR) InGaAs photodetectors;
• Lattice-mismatch material design and epitaxial growth;
• Extended wavelength InGaAs photodetectors;
• Misfit dislocation mitigation technologies ;
• InGaAs focal plane arrays (FPAs);
• Large array format and fine pixel pitch FPAs;
• SWIR read-out integrated circuit (ROIC) designs;
• Application exploration of InGaAs photodetectors;
• Polarization-integrated InGaAs photodetectors;
• SWIR spectral imaging;
• NIR-I and NIR-II biology and medical diagnostics;
• SWIR image processing.

Dr. Yingjie Ma
Guest Editor

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