New research on ultra-thin InGaAs photodetector

New research on ultra-thin InGaAs photodetector
The advancement of short-wave infrared (SWIR) imaging technology has made significant contributions to night vision systems, industrial inspection, scientific research, and security protection and other fields. With the increasing demand for detection beyond the visible light spectrum, the development of short-wave infrared image sensors is also constantly increasing. However, achieving high-resolution and low-noise wide-spectrum photodetector still faces many technical challenges. Although traditional InGaAs short-wave infrared photodetector can exhibit excellent photoelectric conversion efficiency and carrier mobility, there is a fundamental contradiction between their key performance indicators and device structure. To obtain a higher quantum efficiency (QE), conventional designs require an absorption layer (AL) of 3 micrometers or more, and this structural design leads to various problems.
In order to reduce the thickness of the absorption layer (TAL) in InGaAs short-wave infrared photodetector, compensating for the reduction in absorption at long wavelengths is crucial, especially when the small-area absorption layer thickness leads to insufficient absorption in the long-wavelength range. Figure 1a illustrates the method of compensating for the small-area absorption layer thickness by extending the optical absorption path. This study enhances the quantum efficiency (QE) in the short-wave infrared band by introducing a TiOx/Au-based guided mode resonance (GMR) structure on the back side of the device.

Compared with traditional planar metal reflection structures, the guided mode resonance structure can generate multiple resonance absorption effects, significantly enhancing the absorption efficiency of long-wavelength light. Researchers optimized the key parameter design of the guided mode resonance structure, including the period, material composition, and filling factor, through the rigorous coupled-wave analysis (RCWA) method. As a result, this device still maintains efficient absorption in the short-wave infrared band. By leveraging the advantages of InGaAs materials, the researchers also explored the spectral response depending on the substrate structure. The decrease in the thickness of the absorption layer should be accompanied by a decrease in EQE.
In conclusion, this research successfully developed an InGaAs detector with a thickness of only 0.98 micrometers, which is more than 2.5 times thinner than the traditional structure. At the same time, it maintains a quantum efficiency of over 70% in the 400-1700 nm wavelength range. The breakthrough achievement of the ultra-thin InGaAs photodetector provides a new technical path for the development of high-resolution, low-noise wide-spectrum image sensors. The rapid carrier transport time brought by the ultra-thin structure design is expected to significantly reduce electrical crosstalk and improve the response characteristics of the device. At the same time, the reduced device structure is more suitable for single-chip three-dimensional (M3D) integration technology, laying the foundation for achieving high-density pixel arrays.